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  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>Woodstock, NY Artificial Intelligence in Education
Tokyo, Japan, July</journal-title>
      </journal-title-group>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>Curio: An On-Demand Help-Seeking System on iTextbooks for Accelerating Research on Educational Recommendation Algorithms</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Ying-Jui Tseng</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Yu-Hsin Lin</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Gautam Yadav</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Norman Bier</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Vincent Aleven</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Carnegie Mellon University</institution>
          ,
          <addr-line>5000 Forbes Ave Pittsburgh PA 15213</addr-line>
          ,
          <country country="US">United States</country>
        </aff>
      </contrib-group>
      <pub-date>
        <year>2023</year>
      </pub-date>
      <volume>7</volume>
      <issue>2023</issue>
      <fpage>07</fpage>
      <lpage>11</lpage>
      <abstract>
        <p>The emergence of intelligent textbooks (iTextbooks) has broadened the landscape of education, yet poses new challenges in meeting the needs of diverse learners. In response to these challenges, we developed Curio, a personalized educational recommendation system for help-seeking embedded within iTextbooks. By using video transcripts and text extracted from images in iTextbooks as an index for a search engine, Curio provides targeted and context-specific content to aid comprehension. Integrated within the iTextbooks itself, this on-demand tool ofers instant clarification on complex STEM concepts, making learning more adaptable to individual needs. We have been working with Open Learning Initiative (OLI) to refine and test Curio's potential, and envisage its application across various iTextbook platforms. This paper discusses Curio's contribution to the educational recommendation algorithms ifeld.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Self-paced Learning</kwd>
        <kwd>Personalized E-learning</kwd>
        <kwd>Intelligent Textbooks</kwd>
        <kwd>Help-Seeking</kwd>
        <kwd>Recommendation Systems</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        The transition from traditional textbooks to intelligent textbooks (iTextbooks) has democratized
access to education on an unprecedented scale [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. However, with increased accessibility
comes greater learner diversity among learners, with varying levels of prior knowledge and
learning goals. This diversity poses a significant challenge to online learning. The current
lack of personalized scafolding for video learning, particularly in STEM fields, exacerbates
the issue. STEM concepts are often interdependent, with formulas and code often sitting at
the intersection between related concepts. For novice learners, these representations are a
particular challenge, presenting what is often quite literally a new language that is exceptionally
dense – formulas, for example, often succinctly encapsulate expert-level skills and knowledge.
We focus on these representations because they often form real barriers; learners may struggle
to continue their learning if they cannot grasp a single formula or line of code. The current
help-seeking mechanisms, such as discussion forums, have low engagement levels due to a lack
of timely feedback [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ]. External search engines and video platforms such as YouTube are often
used, but they can be unreliable and non-educational information in the search result produces
extraneous cognitive load [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ].
      </p>
      <p>Curio seeks to address these challenges by recommending learning content within the
learning platform and showing the results in the context of the video player. This approach
simultaneously reduces the friction of leaving the platform while ensuring the quality of search
results. Moreover, the tool can leverage the context of the question and the learner model
to filter on-demand recommendations to individual learners’ current needs, making learning
experiences more personalized. By lowering barriers to help-seeking, Curio aims to not only
improve domain-specific learning outcomes but also increase learners’ self-eficacy.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Background</title>
      <sec id="sec-2-1">
        <title>2.1. Help Seeking in Interactive Learning Environments</title>
        <p>
          In interactive learning environments (ILEs), help-seeking is a pivotal strategy that promotes the
development of independent skills and abilities [
          <xref ref-type="bibr" rid="ref4 ref5 ref6">4, 5, 6</xref>
          ]. Context-sensitive help content in ILEs
may provide higher quality assistance than peer helpers . [
          <xref ref-type="bibr" rid="ref7">7</xref>
          ].
        </p>
        <p>
          Help-seeking involves a series of processes, such as becoming aware of the need for help,
deciding to seek help, identifying potential helpers, using strategies to elicit help, and evaluating
the help-seeking episode [
          <xref ref-type="bibr" rid="ref5 ref6 ref8">5, 6, 8</xref>
          ]. Furthermore, placing help under the control of the learner
is likely to improve the timing of the explanations, making them most useful for constructing
new knowledge [
          <xref ref-type="bibr" rid="ref9">9</xref>
          ]. Help-seeking efort can be reduced by impacting variables that mediate the
relations between prior knowledge and help-seeking. [
          <xref ref-type="bibr" rid="ref7">7</xref>
          ]. Adaptive ILEs that minimize demands
on students’ help-seeking skills can be beneficial, especially in iTextbooks that inherently
demand these skills.
        </p>
        <p>
          Existing help-seeking mechanisms in digital learning environments, such as discussion
forums, have low levels of engagement [
          <xref ref-type="bibr" rid="ref10">10</xref>
          ]. In response, the majority of students resort to
existing resources like books and search engines for problem-solving, thus suggesting the
need for exploring alternative methods of providing support to learners, such as content
recommendation [
          <xref ref-type="bibr" rid="ref11">11</xref>
          ].
        </p>
      </sec>
      <sec id="sec-2-2">
        <title>2.2. Search in Learning Context</title>
        <p>
          While search engines have been valuable tools in educational contexts, there is a pressing need
to curtail the cognitive overload that learners experience from non-educational snippets in
search engine result pages [
          <xref ref-type="bibr" rid="ref3">3</xref>
          ]. This can be achieved by only presenting educational content in
our proposed system.
        </p>
        <p>Furthermore, research is sparse on the optimization of extraction and ranking algorithms in
search engines based on learning needs. No current algorithm is interested in determining the
learner knowledge level from the request or the elimination of non-educational content from
search engines.</p>
      </sec>
      <sec id="sec-2-3">
        <title>2.3. Educational Recommendation Systems</title>
        <p>
          Educational recommendation systems have received substantial attention over the years, with
research investigating various aspects such as machine learning-based recommendation systems
for e-learning [
          <xref ref-type="bibr" rid="ref12">12</xref>
          ], ontology-based recommender systems for e-learning [
          <xref ref-type="bibr" rid="ref13">13</xref>
          ], and recommender
systems to support learners’ agency in a learning context [
          <xref ref-type="bibr" rid="ref14">14</xref>
          ].
        </p>
        <p>
          Educational recommendation systems that adapt to students’ existing knowledge of specific
domain concepts have demonstrated eficacy in delivering personalized scafolding within
iTextbooks [
          <xref ref-type="bibr" rid="ref15">15</xref>
          ]. For example, researchers have constructed a Wikipedia recommendation
interface within the digital textbook system to provide learners with alternate educational
resources. This system aids learners in gaining prerequisite knowledge when they struggle
with a particular question [
          <xref ref-type="bibr" rid="ref16">16</xref>
          ].
        </p>
      </sec>
      <sec id="sec-2-4">
        <title>2.4. Learner Modeling</title>
        <p>
          Learner modeling is a key aspect of adaptive learning systems, encapsulating the systems’
assumptions about a learner’s unique attributes related to educational processes [
          <xref ref-type="bibr" rid="ref17">17</xref>
          ]. These
models can account for various learner characteristics, such as demographic information,
knowledge level, cognitive characteristics, social attributes, personality traits, and motivation
factors [
          <xref ref-type="bibr" rid="ref18">18, 19</xref>
          ]. Recent literature reviews highlight the growing interest in this area and the
diversity of techniques used for learner modeling, such as machine learning techniques, Bayesian
Knowledge Tracing (BKT) [20], and other hybrid models.
        </p>
        <p>For instance, the Skills Map learner model of OLI platform applies BKT to classify learners’
knowledge into states of ’learned’ or ’not learned’[21]. This method delineates probabilities for
learners’ responses premised on their comprehension of a concept[22].</p>
        <p>Curio functions as an extensible tool capable of integrating learner models within iTextbook
platforms to further personalize content recommendations for help-seeking. For example, we
intend to incorporate the Skill Map model from the OLI platform to enhance the relevance of
video recommendations based on a learner’s prior knowledge. If a learner has successfully
mastered a skill, Curio’s recommendation algorithm will prioritize videos that do not pertain to
this skill. Conversely, if the learner is in the process of understanding a skill, the system will
prioritize videos relevant to that skill, thereby assisting the learner in grasping the concept.</p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>3. User Interface</title>
      <p>The Curio user interface is a comprehensive solution designed to enhance the e-learning
experience by being implemented as an overlay atop any video player or text within various
learning platforms. It has been structured to facilitate easy access to learning resources, promote
interactivity, and provide tailored explanations for students’ misconceptions.</p>
      <sec id="sec-3-1">
        <title>3.1. In-Widget Recommendation Result</title>
        <p>Curio’s In-Widget Recommendation feature serves as a powerful tool that provides learners
with a range of educational resources directly within the platform. The feature operates by
analyzing the content currently being viewed by the learner and generates relevant educational
materials to supplement their learning. These results, organized according to their relevance to
the current learning context, are directly presented to the learners within the video player (see
Figure 1) or text interface, without necessitating a disruptive shift to a new page or platform.</p>
      </sec>
      <sec id="sec-3-2">
        <title>3.2. Concept Description</title>
        <p>Curio takes advantage of large language models (LLM) to supplement the recommendation
results, specifically integrating GPT-4 to provide text-based instructions. This feature targets
students’ misconceptions, delivering tailored guidance to clarify their understanding and address
gaps in their knowledge. We crafted a example result and explicly providde regulations to the
GPT-4 endpoint, to ensure the quality of generated summaries. The main prompt body we used
in the query is</p>
        <p>What’s the definition of $text related to $learningObj in a course $courseName?
By implementing the few-shot prompting technique and supplying the context of the learning
material the learner is seeking help with as variables in the GPT-4 prompt, Curio is equipped to
deliver context-specific, real-time explanations for any term, formula, and code snippets within
iTextbooks.</p>
      </sec>
      <sec id="sec-3-3">
        <title>3.3. Collection Feature</title>
        <p>The Collection Feature in Curio is designed to facilitate personalized learning by allowing
learners to earmark specific resources for future reference. This feature is particularly advantageous
for learners who discover relevant materials that they wish to revisit later. This ability to curate
learning resources based on individual needs further enhances the personalization capabilities
of Curio.</p>
        <p>User
Reverse Proxy
(Nginx)</p>
        <p>Frontend (React.js)
API Server (Koa.js)</p>
        <p>DB
(MongoDB)</p>
        <p>Course Texts
(Elasticsearch)
Curio Preprocessor</p>
        <p>Analyzer
(PyTesseract)
Static Files &amp;
Course Videos</p>
        <p>Formatter
(Python)
Course Subtitles</p>
        <p>Course Videos</p>
        <p>In summary, the Curio user interface serves as an embedded help-seeking tool within learning
platforms. It provides on-demand, uninterrupted access to tailored educational resources, thus
ofering personalized scafolding for learners according to their unique needs.</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. System Implementation</title>
      <p>The primary objective of Curio’s system implementation is to address three key technical
challenges that may hinder users in their quest to comprehend learning contents on the platform.
The first challenge is how to efectively index all teaching materials available on the platform.
The second challenge is how to guide users in conducting efective searches with appropriate
keywords. Lastly, the third challenge is how to ensure that when users query the platform, they
do not receive excessive false positives.</p>
      <p>To tackle the first challenge, we employed Tesseract v5.0 [ 23], an open-source LSTM-based
OCR solution. This solution enables us to scan the video frame every few seconds and extract
all text, source code, and formulae displayed on the screen. We store this information, along
with subtitles and timecodes, in Elasticsearch [24], which facilitates full-text searching.</p>
      <p>Additionally, we integrated the Tesseract engine into our video player with the same
configurations, which enables students to initiate searches by using a selection tool on the interface
and encourages them to search with the same vocabulary set stored in the Elasticsearch server.</p>
      <p>Lastly, to mitigate the risk of false positives, we apply a weight calculated based on the
learner’s current proficiency on prerequisites, ensuring that users receive relevant learning
materials. Currently, we are testing the platform with a simpler version of algorithm (
indicates whether a returned video share the same learning object with current video or not):
newScore = (1 · (1 −  ) + 2 ·  ) · originalScore
While advanced learner models have not been integrated, Curio was intentionally designed as
an extensible approach capable of accommodating such enhancements. This design allows for
further improvements to the search results by incorporating advanced learner models if desired.</p>
    </sec>
    <sec id="sec-5">
      <title>5. Future Work</title>
      <p>Curio aims to accelerate learning science research by empowering researchers to experiment
with diferent educational recommendation algorithms and collect valuable help-seeking data
that is traditionally dificult to measure. Research on optimization of extraction and ranking
algorithms based on learning needs is relatively rare, and existing algorithms do not aim to
determine the learner’s knowledge level from the request. Curio can address this issue by
enabling researchers and developers to experiment with diferent educational recommendation
algorithms on both established platforms and research prototypes, facilitating data collection.
Researchers can import platform- or lesson-specific video metadata and learner models into
Curio’s Elasticsearch service and try out diferent weights to optimize recommendation strategies
for specific research questions.</p>
      <p>In addition to accelerating research in educational recommendation algorithms, Curio can
help researchers and educators gain insights into learner’s help-seeking behavior. One of the
major challenges in measuring the help-seeking behavior of iTextbook learners is that it often
happens on external platforms like Google search and YouTube. Curio ofers a solution by
recommending learning content within the iTextbook, enabling researchers to gain insights
into learners’ help-seeking behaviors and providing guidelines for optimal educational content
recommendation strategies. Additionally, the help-seeking data collected by Curio can serve as
a supplement to measure iTextbook learners’ self-regulation, agency, and curiosity, which are
nowadays measured by self-report questionnaires that raise concerns about susceptibility to
bias.</p>
      <p>The data collected by Curio will be openly published and uploaded to DataShop, an
opensourced repository for sharing and analyzing data on the interactions between students and
educational software. Furthermore, researchers who utilize Curio for research can also collect
and share the help-seeking data they collect with our data pipeline and infrastructure.
learner modeling techniques, User Modeling and User-Adapted Interaction 27 (2017)
313–350.
[19] K. Seta, Y. Taniguchi, M. Ikeda, Learner modeling to capture meta-cognitive activities
through presentation design, the Journal of Information and Systems in Education 14
(2015) 1–12.
[20] S. Bulathwela, M. Pérez-Ortiz, E. Yilmaz, J. Shawe-Taylor, Semantic truelearn: Using
semantic knowledge graphs in recommendation systems, arXiv preprint arXiv:2112.04368
(2021).
[21] N. Bier, S. Lip, R. Strader, C. Thille, D. Zimmaro, An approach to knowledge component/skill
modeling in online courses, Open Learning (2014) 1–14.
[22] M. V. Yudelson, K. R. Koedinger, G. J. Gordon, Individualized bayesian knowledge tracing
models, in: Artificial Intelligence in Education: 16th International Conference, AIED 2013,
Memphis, TN, USA, July 9-13, 2013. Proceedings 16, Springer, 2013, pp. 171–180.
[23] GitHub - tesseract-ocr/tesseract: Tesseract Open Source OCR Engine (main repository) —
github.com, https://github.com/tesseract-ocr/tesseract, 2023. [Accessed 20-May-2023].
[24] Elastic, Elastic/elasticsearch: Free and open, distributed, restful search engine, 2023. URL:
https://github.com/elastic/elasticsearch, [Accessed 20-May-2023].</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          [1]
          <string-name>
            <given-names>P.</given-names>
            <surname>Brusilovsky</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Sosnovsky</surname>
          </string-name>
          ,
          <string-name>
            <given-names>K.</given-names>
            <surname>Thaker</surname>
          </string-name>
          ,
          <article-title>The return of intelligent textbooks</article-title>
          ,
          <source>AI</source>
          Magazine
          <volume>43</volume>
          (
          <year>2022</year>
          )
          <fpage>337</fpage>
          -
          <lpage>340</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          [2]
          <string-name>
            <given-names>L.</given-names>
            <surname>Corrin</surname>
          </string-name>
          ,
          <string-name>
            <surname>P. G. De Barba</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          <string-name>
            <surname>Bakharia</surname>
          </string-name>
          ,
          <article-title>Using learning analytics to explore help-seeking learner profiles in moocs</article-title>
          ,
          <source>in: Proceedings of the seventh international learning analytics &amp; knowledge conference</source>
          ,
          <year>2017</year>
          , pp.
          <fpage>424</fpage>
          -
          <lpage>428</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          [3]
          <string-name>
            <given-names>J. K.</given-names>
            <surname>Homte</surname>
          </string-name>
          ,
          <string-name>
            <given-names>B.</given-names>
            <surname>Batchakui</surname>
          </string-name>
          ,
          <string-name>
            <given-names>R.</given-names>
            <surname>Nkambou</surname>
          </string-name>
          ,
          <article-title>Search engines in learning contexts: A literature review</article-title>
          ,
          <source>International Journal of Emerging Technologies in Learning (iJET) 17</source>
          (
          <year>2022</year>
          )
          <fpage>254</fpage>
          -
          <lpage>272</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          [4]
          <string-name>
            <given-names>R.</given-names>
            <surname>Ames</surname>
          </string-name>
          ,
          <article-title>Help-seeking and achievement orientation: Perspectives from attribution theory, New directions in helping 2 (</article-title>
          <year>1983</year>
          )
          <fpage>165</fpage>
          -
          <lpage>186</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          [5]
          <string-name>
            <given-names>S.</given-names>
            <surname>Nelson-Le</surname>
          </string-name>
          <string-name>
            <surname>Gall</surname>
          </string-name>
          ,
          <article-title>Help-seeking: An understudied problem-solving skill in children</article-title>
          ,
          <source>Developmental review 1</source>
          (
          <year>1981</year>
          )
          <fpage>224</fpage>
          -
          <lpage>246</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          [6]
          <string-name>
            <given-names>R. S.</given-names>
            <surname>Newman</surname>
          </string-name>
          ,
          <article-title>Adaptive help seeking: A strategy of self-regulated learning, Self-regulation of learning and performance: Issues and educational applications (</article-title>
          <year>1994</year>
          )
          <fpage>283</fpage>
          -
          <lpage>301</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          [7]
          <string-name>
            <given-names>V.</given-names>
            <surname>Aleven</surname>
          </string-name>
          , E. Stahl,
          <string-name>
            <given-names>S.</given-names>
            <surname>Schworm</surname>
          </string-name>
          ,
          <string-name>
            <given-names>F.</given-names>
            <surname>Fischer</surname>
          </string-name>
          ,
          <string-name>
            <given-names>R.</given-names>
            <surname>Wallace</surname>
          </string-name>
          ,
          <article-title>Help seeking and help design in interactive learning environments</article-title>
          ,
          <source>Review of educational research 73</source>
          (
          <year>2003</year>
          )
          <fpage>277</fpage>
          -
          <lpage>320</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          [8]
          <string-name>
            <given-names>M.</given-names>
            <surname>Puustinen</surname>
          </string-name>
          ,
          <article-title>Help-seeking behavior in a problem-solving situation: Development of self-regulation</article-title>
          ,
          <source>European Journal of Psychology of education 13</source>
          (
          <year>1998</year>
          )
          <fpage>271</fpage>
          -
          <lpage>282</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          [9]
          <string-name>
            <given-names>A.</given-names>
            <surname>Renkl</surname>
          </string-name>
          ,
          <article-title>Worked-out examples: Instructional explanations support learning by selfexplanations</article-title>
          ,
          <source>Learning and instruction 12</source>
          (
          <year>2002</year>
          )
          <fpage>529</fpage>
          -
          <lpage>556</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref10">
        <mixed-citation>
          [10]
          <string-name>
            <given-names>D.</given-names>
            <surname>Onah</surname>
          </string-name>
          ,
          <string-name>
            <given-names>J.</given-names>
            <surname>Sinclair</surname>
          </string-name>
          ,
          <article-title>Assessing self-regulation of learning dimensions in a stand-alone mooc platform (</article-title>
          <year>2017</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref11">
        <mixed-citation>
          [11]
          <string-name>
            <given-names>D.</given-names>
            <surname>Davis</surname>
          </string-name>
          , G. Chen,
          <string-name>
            <given-names>C.</given-names>
            <surname>Hauf</surname>
          </string-name>
          ,
          <string-name>
            <given-names>G.-J.</given-names>
            <surname>Houben</surname>
          </string-name>
          ,
          <article-title>Activating learning at scale: A review of innovations in online learning strategies</article-title>
          ,
          <source>Computers &amp; Education</source>
          <volume>125</volume>
          (
          <year>2018</year>
          )
          <fpage>327</fpage>
          -
          <lpage>344</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref12">
        <mixed-citation>
          [12]
          <string-name>
            <given-names>A.</given-names>
            <surname>Klašnja-Milićević</surname>
          </string-name>
          ,
          <string-name>
            <given-names>B.</given-names>
            <surname>Vesin</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Ivanović</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Z.</given-names>
            <surname>Budimac</surname>
          </string-name>
          ,
          <string-name>
            <given-names>L. C.</given-names>
            <surname>Jain</surname>
          </string-name>
          ,
          <string-name>
            <given-names>A.</given-names>
            <surname>Klašnja-Milićević</surname>
          </string-name>
          ,
          <string-name>
            <given-names>B.</given-names>
            <surname>Vesin</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M.</given-names>
            <surname>Ivanović</surname>
          </string-name>
          ,
          <string-name>
            <given-names>Z.</given-names>
            <surname>Budimac</surname>
          </string-name>
          ,
          <string-name>
            <given-names>L. C.</given-names>
            <surname>Jain</surname>
          </string-name>
          ,
          <article-title>Recommender systems in e-learning environments, E-learning systems: Intelligent techniques for personalization (</article-title>
          <year>2017</year>
          )
          <fpage>51</fpage>
          -
          <lpage>75</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref13">
        <mixed-citation>
          [13]
          <string-name>
            <given-names>H.</given-names>
            <surname>Drachsler</surname>
          </string-name>
          ,
          <string-name>
            <given-names>K.</given-names>
            <surname>Verbert</surname>
          </string-name>
          ,
          <string-name>
            <given-names>O. C.</given-names>
            <surname>Santos</surname>
          </string-name>
          ,
          <string-name>
            <given-names>N.</given-names>
            <surname>Manouselis</surname>
          </string-name>
          ,
          <article-title>Panorama of recommender systems to support learning, Recommender systems handbook (</article-title>
          <year>2015</year>
          )
          <fpage>421</fpage>
          -
          <lpage>451</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref14">
        <mixed-citation>
          [14]
          <string-name>
            <given-names>J. L.</given-names>
            <surname>Santos</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Govaerts</surname>
          </string-name>
          ,
          <string-name>
            <given-names>K.</given-names>
            <surname>Verbert</surname>
          </string-name>
          , E. Duval,
          <article-title>Goal-oriented visualizations of activity tracking: a case study with engineering students</article-title>
          ,
          <source>in: Proceedings of the 2nd international conference on learning analytics and knowledge</source>
          ,
          <year>2012</year>
          , pp.
          <fpage>143</fpage>
          -
          <lpage>152</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref15">
        <mixed-citation>
          [15]
          <string-name>
            <given-names>K.</given-names>
            <surname>Thaker</surname>
          </string-name>
          ,
          <string-name>
            <given-names>L.</given-names>
            <surname>Zhang</surname>
          </string-name>
          ,
          <string-name>
            <given-names>D.</given-names>
            <surname>He</surname>
          </string-name>
          ,
          <string-name>
            <given-names>P.</given-names>
            <surname>Brusilovsky</surname>
          </string-name>
          ,
          <article-title>Recommending remedial readings using student knowledge state</article-title>
          .,
          <source>International Educational Data Mining Society</source>
          (
          <year>2020</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref16">
        <mixed-citation>
          [16]
          <string-name>
            <given-names>B.</given-names>
            <surname>Rahdari</surname>
          </string-name>
          ,
          <string-name>
            <given-names>P.</given-names>
            <surname>Brusilovsky</surname>
          </string-name>
          ,
          <string-name>
            <given-names>K.</given-names>
            <surname>Thaker</surname>
          </string-name>
          ,
          <string-name>
            <given-names>J.</given-names>
            <surname>Barria-Pineda</surname>
          </string-name>
          ,
          <article-title>Knowledge-driven wikipedia article recommendation for electronic textbooks</article-title>
          ,
          <source>in: Addressing Global Challenges and Quality Education: 15th European Conference on Technology Enhanced Learning, EC-TEL</source>
          <year>2020</year>
          , Heidelberg, Germany,
          <source>September 14-18</source>
          ,
          <year>2020</year>
          , Proceedings 15, Springer,
          <year>2020</year>
          , pp.
          <fpage>363</fpage>
          -
          <lpage>368</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref17">
        <mixed-citation>
          [17]
          <string-name>
            <given-names>A.</given-names>
            <surname>Abyaa</surname>
          </string-name>
          ,
          <string-name>
            <given-names>M. Khalidi</given-names>
            <surname>Idrissi</surname>
          </string-name>
          ,
          <string-name>
            <given-names>S.</given-names>
            <surname>Bennani</surname>
          </string-name>
          ,
          <article-title>Learner modelling: systematic review of the literature from the last 5 years</article-title>
          ,
          <source>Educational Technology Research and Development</source>
          <volume>67</volume>
          (
          <year>2019</year>
          )
          <fpage>1105</fpage>
          -
          <lpage>1143</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref18">
        <mixed-citation>
          [18]
          <string-name>
            <given-names>R.</given-names>
            <surname>Pelánek</surname>
          </string-name>
          ,
          <article-title>Bayesian knowledge tracing, logistic models, and beyond: an overview of</article-title>
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>