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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Author Gender Prediction in Russian Social Media Texts</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Tatiana Litvinova</string-name>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Dmitry Gudovskikh</string-name>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Аlexandr Sboev</string-name>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Pavel S</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Litvinov</string-name>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Independent researcher</institution>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>PRHLT Research Center, Universitat Politècnica de València</institution>
          ,
          <country country="ES">Spain</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>The Kurchatov Institute</institution>
          ,
          <country country="RU">Russia</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>Presently natural language processing for social media, in particular in the field of sentiment analysis and topic modeling, is gaining momentum for Russian texts. However, Slavic languages including Russian are still insufficiently explored in terms of computational sociolinguistics and authorship profiling (i.e. automatic identification of latent demographic features of online users such as gender, age, personality based on their texts). Being able to predict these features with a high degree of accuracy would certainly benefit marketing, psychological studies and security. In this paper we are attempting to build classifiers to predict gender of the author in Russian Twitter and Facebook texts and explore the effect of the cross-genre evaluation. We used the most common lemmas, a set of morphological and syntactic parameters as well as the part-ofspeech (POS) trigrams as features and multiple classifiers to train and test models. Twitter corpus was used for training, Facebook and test set of Twitter corpus were used for testing. The best models for Twitter were ExtraTreesClassifier and RandomForestClassifier with accuracy 0.72 and linearSVM for Facebook (0.71). The obtained results are comparable with stateof-the art results for Russian language for the texts of different genres.</p>
      </abstract>
      <kwd-group>
        <kwd>Computational sociolinguistics</kwd>
        <kwd>Russian social media texts</kwd>
        <kwd>Gender attribution</kwd>
        <kwd>POS n-grams</kwd>
        <kwd>Text categorization</kwd>
        <kwd>Twitter</kwd>
        <kwd>Facebook</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>Problem statement</title>
      <p>The rapid growth of social media in recent years, exemplified by Facebook and
Twitter, has led to a massive volume of user-generated informal text. This in turn has
sparked a great deal of research interest in aspects of social media, including
automatically identifying latent demographic features of online users. Many latent features
have been explored, but gender and age have generated great interest. Accurate
prediction of these features would be useful for marketing and personalization concerns,
as well as for security. The majority of recent work in this area has focused on Twitter
users [2; 3; 10]. Gender inference accuracy has been reported between 80% and 85%.</p>
      <p>
        Gender prediction is one of the tasks which PAN (a series of scientific events and
shared tasks on digital text forensics) participants solve1 [9; 10]. However advances in
latent attribute inference on social media have been largely confined to English
content. Gender profiling for social media texts has not been sufficiently researched using
Slavic languages except a recent study of the Slovenian language [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ]. As for the
Russian language, there has been a lot of progress made in social media sentiment
analysis [8; 14], topic modeling [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ], but to the best of our knowledge, there have been
no attempts made to extract social media text author demographics by analyzing their
texts with except for work Korshunov et al. [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ] who used only token N-grams (N=
13) as features and tweets of rather small number of users (450 in total) for training.
Besides, they do not describe their corpus in detail.
      </p>
      <p>
        Russian written texts were investigated in the context of author profiling, including
gender prediction. Using RusPersonality corpus which consists of the texts of
different genres (e.g. description of a picture, essays on different topics, etc.) labeled with
information on their authors (gender, age, results of psychological tests, and so on)
authors of [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] obtained models with different F1, 0.74 being the best (ReLU, 1
Hidden Layer with 26 neurons).
      </p>
      <p>
        The objective of the current paper is to build classifiers for identifying gender of
authors of Twitter and Facebook texts in Russian using different algorithms and
compare their accuracies. Following PAN 2016 framework [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ], we aim at investigating
the effect of the cross-genre evaluation, so that models are trained on one genre,
which is Twitter here, and evaluated on another genre different from Twitter
(Facebook) since it is well-known that “models trained on one genre may not give the same
pattern of performance if they are evaluated on a data set, which contains author
profiles from a different genre” [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ].
2
2.1
      </p>
    </sec>
    <sec id="sec-2">
      <title>Materials and methods</title>
    </sec>
    <sec id="sec-3">
      <title>Material</title>
      <p>
        Twitter. Annotating social media texts is what makes designing such corpora
particularly challenging. Some researchers automatically built Twitter corpora while others
have solved this problem by using labor-intensive methods. For example, Rao et al.
[
        <xref ref-type="bibr" rid="ref11">11</xref>
        ] use a focused search methodology followed by manual annotation to produce a
dataset of 500 English users labeled with gender. The gender tag was ascribed based
on the screen name, profile picture, self-description (’bio’) and – in the few cases that
this was not sufficient – the use of gender markings when referring to themselves. For
this research we used the same approach with manual labeling for tweet author
gen1 http://pan.webis.de/clef17/pan17-web/author-profiling.html,
http://pan.webis.de/clef16/pan16web/author-profiling.html
der. For those cases where the gender information was not clear, we discarded the
user. API-query was made for 200 posts, i.e. over 1000 words from each user.
Retweets were removed2.
      </p>
      <p>Facebook. 228 users of different age groups (20+, 30+, 40+) from different cities
and occupations were randomly chosen (to get minimum mutual friendships) with no
less than 1000 words per user.</p>
      <p>Corpus statistics is presented in Table 1.</p>
      <p>The general principles of processing the text corpora are as follows:
1. Non-Russian texts were removed;
2. Citations were removed;
3. Accounts of public people were not used as they might have someone else
writing for them;
4. http references were removed.
5. All hashtags (marked with #) were replaced with the «hashtag» tag;
6. Named entities (marked with @) are replaced with the NER tag.
Source Мale users Female users
Twitter 543 543</p>
      <p>Facebook 114 114</p>
      <p>
        Given that the most frequent terms tend to select the most discriminative features
when applied to stylistic studies [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ], first of all we identified the most frequent
lemmas for each class. As was shown in [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ], morphological and syntactic features are
important for gender prediction. Part-of-speech (POS) N-grams were shown to be
especially effective since they can efficiently encode syntactical information. Below
we discuss our feature sets in more detail.
      </p>
      <p>
        1) top 250 lemmas. We used 250 most frequent lemmas in the corpus. Note that we
chose to employ lemmas as Russian is a morphologically rich language where gender
is expressed explicitly in a range of grammatical structures. However, grammatical
gender markings are easily falsified. As we have in mind as a general goal to build a
system for gender prediction efficient, even in the case of gender imitation (valuable
for security reasons), we made a decision to avoid using the token-based approach.
For lemmatization we use Mystem [
        <xref ref-type="bibr" rid="ref13">13</xref>
        ], a freely available stemmer for Russian;
2) we used a set of morphological (the frequencies of POS), syntactical features
(frequencies of different types of syntactic relationships between heads and
dependents3) and psycholinguistic markers (derivative coefficients which reflect different
ratios of POS), 56 in total;
2 Twitter corpus is available at http://en.rusprofilinglab.ru/rusprofiling-at-pan/korpus/ Last
visited 04/07/2017
3 We used SynTagRus corpus tag system, http://www.ruscorpora.ru/instruction-syntax.html,
https://github.com/UniversalDependencies/UD_Russian-SynTagRus
      </p>
      <p>3) we have chosen top 15 frequent POS trigrams which averaged values are
different in males and female texts. At the first stage we chose POS trigrams which
occurred in 75 % of the documents of the class and then calculated the difference
between the average values of the frequencies of POS trigrams in texts by males and
females and as a result, 15 POS trigrams with the largest difference in the average
values were selected.</p>
      <p>The values of all the properties were normalized either by the number of words in
the documents or that of POS trigrams.</p>
      <p>The majority of prior work in gender inference (and latent inference in general) has
used support vector machine (SVM). We explored multiple classifiers from the
scikitlearn Python library to train and test our models. The training was conducted using
cross-validation for 30 folds by means of StratifiedKFold strategies. The Twitter
corpus was divided into the training (90 %) and test (10 %) sets. Twitter was used for
training; Twitter test set and the whole Facebook corpus were used for testing.
3</p>
    </sec>
    <sec id="sec-4">
      <title>Results and discussion</title>
      <p>
        The classification results are presented in Table 2. The results listed in the tables are
average values of each “training-testing” cycle.
ing with Twitter where people share their comments without censorship, in a
spontaneous way, and where researchers can obtain a high number of texts per author, could
be a good manner to improve the performance of author profiling tasks in other
genres (such as blogs) for which it is more difficult to obtain sufficient training data”
[
        <xref ref-type="bibr" rid="ref10">10</xref>
        ].
      </p>
      <p>The analysis of the frequencies of linguistic parameters enabled us to make some
interesting observations (cf. [5; 8]) (t-test was used, p  0.05). More frequent
character flooding (greaaattt (“отлиичноо”), oomph (“уффффф”), hurray (“урраааа”),
theyyy “онииии”), diminutives (referring to men and food), named entity mentions
(marked with @) are typical for female Twitter texts. As for Facebook, woman tend
to use more specific geographic and proper names, as well as mention clothes, family
and religious more often than males. In male Facebook texts there are more military,
drinking, computer, food, car vocabulary.</p>
      <p>
        For Twitter and Facebook texts the following are common: females tend to use the
conjunctions “and” («и»/«а»), negations “not” («не»), significantly more pronouns
“I” («я»), “my” («мой»), “own” («свой») as well as relative pronouns “the
whole”(«весь»), “this” («этот»), “such” («такой»), preposition “near” («у»); slightly
more – “we” («мы»), “you” («вы»), “she” («она»), adverb “very” («очень»). Males
prefer the prepositions “in” («в»), “on” («на»), “around” («по»), “about” («о»),
“from” («из»), “for” («для»), conjunction “but” («но»), pronoun “they” («они»). The
fact that pronouns are more common in female texts and prepositions in those by
males is in agreement with the observations made for other languages (for different
text genres), as well as for Russian texts of different genres (see [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ] for details). Note
that these differences are more distinct in Facebook texts.
4
      </p>
    </sec>
    <sec id="sec-5">
      <title>Conclusions and Future Work</title>
      <p>
        The results for prediction of Twitter user gender using most common lemmas and
morphosyntactical parameters as features are comparable to those for Russian offline
texts from the corpus RusPersonality [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ]. Although we trained on Twitter, our models
showed similar accuracies on Facebook texts which means that our feature set is
useful for gender identification in different genres of social media.
      </p>
      <p>Note however that we consciously excluded the gender-marked parameters, which
made the task more challenging. In future we are planning to expand our feature sets
with special attention on content-independent parameters including readability
measures, etc. which are more useful in gender detection designed for real-world
application where users can imitate their writing pretending to be a people of opposite
sex (for example, a pedophile can imitate the writing style of a young girl, to groom a
child, etc.)
Acknowledgment. This research is financially supported by the Russian Science
Foundation, project No 16-18-10050 “Identifying the Gender and Age of Online
Chatters Using Formal Parameters of their Texts”.</p>
      <p>The work of the last author was in the framework of the SomEMBED
TIN201571147-C2-1-P MINECO research project.</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          1.
          <string-name>
            <surname>Ashraf</surname>
            <given-names>S.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Iqbal</surname>
            <given-names>H. R.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Muhammad</surname>
            <given-names>R.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Nawab</surname>
            <given-names>A</given-names>
          </string-name>
          .
          <article-title>Cross-Genre Author Profile Prediction Using Stylometry-Based Approach</article-title>
          . In:
          <article-title>Working Notes Papers of the CLEF 2016 Evaluation Labs</article-title>
          .
          <article-title>CEUR-WS.org</article-title>
          . Évora,
          <string-name>
            <surname>Portugal</surname>
          </string-name>
          (
          <year>2016</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          2.
          <string-name>
            <surname>Burger</surname>
            ,
            <given-names>J.D.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Henderson</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Kim</surname>
            ,
            <given-names>G.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Zarrella</surname>
          </string-name>
          , G.:
          <article-title>Discriminating gender on Twitter</article-title>
          .
          <source>In: Proceedings of the Conference on Empirical Methods in Natural Language Processing</source>
          , pp.
          <fpage>1301</fpage>
          -
          <lpage>1309</lpage>
          . Edinburgh, United Kingdom.
          <source>ACM</source>
          (
          <year>2011</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          3.
          <string-name>
            <surname>Ciot</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Sonderegger</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Ruths</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          <article-title>Gender inference of Twitter users in non-English contexts</article-title>
          .
          <source>In: Proceedings of the Conference on Empirical Methods in Natural Language Processing</source>
          , pp.
          <fpage>1136</fpage>
          -
          <lpage>1145</lpage>
          (
          <year>2013</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          4.
          <string-name>
            <surname>Koltsova</surname>
            ,
            <given-names>O.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Koltcov</surname>
            <given-names>S.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Nikolenko</surname>
            <given-names>S.</given-names>
          </string-name>
          <article-title>Communities of co-commenting in the Russian LiveJournal and their topical coherence</article-title>
          .
          <source>Internet Research</source>
          <volume>26</volume>
          (
          <issue>3</issue>
          ) (
          <year>2016</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          5.
          <string-name>
            <surname>Korshunov</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Beloborodov</surname>
            ,
            <given-names>I.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Gomzin</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Chuprina</surname>
            ,
            <given-names>K.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Astrakhantsev</surname>
            ,
            <given-names>N.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Nedumov</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Turdakov</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          <article-title>Definition of demographic attributes of users of microblogging</article-title>
          ,
          <source>In: Proceedings of the Institute of System Programming</source>
          ,
          <source>Russian Academy of Sciences</source>
          <volume>25</volume>
          <fpage>179</fpage>
          -
          <lpage>194</lpage>
          (
          <year>2013</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          6.
          <string-name>
            <surname>Litvinova</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Seredin</surname>
            ,
            <given-names>P.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Litvinova</surname>
            ,
            <given-names>O.</given-names>
          </string-name>
          <string-name>
            <surname>Zagorovskaya</surname>
          </string-name>
          , O.
          <source>Gender Identification in Russian Written Texts. XLinguae 3</source>
          ,
          <fpage>176</fpage>
          -
          <lpage>183</lpage>
          (
          <year>2017</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          7.
          <string-name>
            <surname>Litvinova</surname>
            ,
            <given-names>T.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Seredin</surname>
            ,
            <given-names>P.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Litvinova</surname>
            ,
            <given-names>O.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Sboev</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Zagorovskaya</surname>
            ,
            <given-names>O.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Gudovskikh</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Moloshnikov</surname>
            ,
            <given-names>I.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Rybka</surname>
            ,
            <given-names>R.</given-names>
          </string-name>
          <article-title>Gender Prediction for Authors of Russian Texts Using Regression and Classification Techniques</article-title>
          .
          <source>Proc. of The Third International Workshop on Concept Discovery in Unstructured Data (CDUD</source>
          <year>2016</year>
          )
          <article-title>: CEUR Workshop Proceedings</article-title>
          . Vol-
          <volume>1625</volume>
          . Moscow, Russia,
          <fpage>44</fpage>
          -
          <lpage>53</lpage>
          (
          <year>2016</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          8.
          <string-name>
            <surname>Loukachevitch</surname>
            ,
            <given-names>N.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Blinov</surname>
            ,
            <given-names>P.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Kotelnikov</surname>
            ,
            <given-names>E.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Rubtsova</surname>
          </string-name>
          , Ju.,
          <string-name>
            <surname>Ivanov</surname>
            ,
            <given-names>V.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Tutubalina</surname>
            ,
            <given-names>H.</given-names>
          </string-name>
          <article-title>Sentirueval: Testing Object-Oriented Sentiment Analysis Systems in Russian</article-title>
          .
          <source>In: Proceedings of International Conference Dialog</source>
          , pp.
          <fpage>3</fpage>
          -
          <lpage>13</lpage>
          . Rossiiskii Gosudarstvennyi Gumanitarnyi Universitet, Moscow, Russia (
          <year>2015</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          9.
          <string-name>
            <surname>Rangel</surname>
            ,
            <given-names>F.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Celli</surname>
            ,
            <given-names>F.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Rosso</surname>
            <given-names>P.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Potthast</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          <string-name>
            <surname>Stein</surname>
            ,
            <given-names>B.</given-names>
          </string-name>
          <string-name>
            <surname>Daelemans</surname>
            ,
            <given-names>W.</given-names>
          </string-name>
          <article-title>Overview of the 3rd Author Profiling Task at PAN 2015</article-title>
          .
          <article-title>In: CLEF 2015 Labs and Workshops, Notebook Papers, CEUR-WS.org</article-title>
          . Toulouse, France (
          <year>2015</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref10">
        <mixed-citation>
          10.
          <string-name>
            <surname>Rangel</surname>
            ,
            <given-names>F.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Rosso</surname>
            <given-names>P.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Verhoeven</surname>
            ,
            <given-names>B.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Daelemans</surname>
            ,
            <given-names>W.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Potthast</surname>
          </string-name>
          , M. Stein B.
          <source>Overview of the 4th Author Profiling Task at PAN</source>
          <year>2016</year>
          :
          <article-title>Cross-Genre Evaluations</article-title>
          .
          <source>In: Working Notes Papers of the CLEF</source>
          <year>2016</year>
          <article-title>Evaluation Labs</article-title>
          .
          <article-title>CEUR-WS.org</article-title>
          . Évora,
          <string-name>
            <surname>Portugal</surname>
          </string-name>
          (
          <year>2016</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref11">
        <mixed-citation>
          11.
          <string-name>
            <surname>Rao</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Yarowsky</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Shreevats</surname>
            ,
            <given-names>A.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Gupta</surname>
            ,
            <given-names>M.</given-names>
          </string-name>
          <article-title>Classifying latent user attributes in twitter</article-title>
          .
          <source>In: Proceedings of the 2nd International Workshop on Search and Mining UserGenerated Contents</source>
          , pp.
          <fpage>37</fpage>
          -
          <lpage>44</lpage>
          . ACM (
          <year>2010</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref12">
        <mixed-citation>
          12.
          <string-name>
            <surname>Savoy</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          <article-title>Comparative Evaluation of Term Selection Functions for Authorship Attribution</article-title>
          .
          <source>Digital Scholarship in the Humanities</source>
          <volume>30</volume>
          (
          <issue>2</issue>
          ),
          <fpage>246</fpage>
          -
          <lpage>261</lpage>
          (
          <year>2015</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref13">
        <mixed-citation>
          13.
          <string-name>
            <surname>Segalovich</surname>
            ,
            <given-names>I.</given-names>
          </string-name>
          <article-title>A fast morphological algorithm with unknown word guessing induced by a dictionary for a web search engine</article-title>
          . In: MLMTA. (
          <year>2003</year>
          )
        </mixed-citation>
      </ref>
      <ref id="ref14">
        <mixed-citation>
          14.
          <string-name>
            <surname>Vasilyev</surname>
            ,
            <given-names>V. G.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Denisenko</surname>
            ,
            <given-names>A. A.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Solovyev</surname>
            ,
            <given-names>D. A.</given-names>
          </string-name>
          <string-name>
            <surname>Aspect</surname>
          </string-name>
          <article-title>Extraction and Twitter Sentiment Classification by Fragment Rules</article-title>
          .
          <source>In Proceedings of International Conference Dialog. Rossiiskii Gosudarstvennyi Gumanitarnyi Universitet</source>
          , Moscow, Russia, рр.
          <fpage>100</fpage>
          -
          <lpage>110</lpage>
          (
          <year>2015</year>
          ).
        </mixed-citation>
      </ref>
      <ref id="ref15">
        <mixed-citation>
          15.
          <string-name>
            <surname>Verhoeven</surname>
            ,
            <given-names>B.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Krjanec</surname>
            ,
            <given-names>I.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Pollak</surname>
            ,
            <given-names>S.</given-names>
          </string-name>
          <article-title>Gender Profiling for Slovene Twitter Communication: The Influence of Gender Marking, Content and Style</article-title>
          .
          <source>Proceedings of the 6th Workshop on Balto-Slavic Natural Language Processing</source>
          , pp.
          <fpage>119</fpage>
          -
          <lpage>125</lpage>
          . Valencia, Spain. ACM (
          <year>2017</year>
          ).
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>