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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>The Role of the Central Executive and Slave Systems of Working Memory in the Insight Problem Solving</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Sergei Yu. Korovkin (korovkin_su@list.ru)</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Alexandra V. Chistopolskaya</institution>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Ilya Yu. Vladimirov</institution>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>P.G. Demidov Yaroslavl State University, Department of Psychology</institution>
          ,
          <addr-line>Proezd Matrosova, 9, Yaroslavl, Russian Federation 150057</addr-line>
        </aff>
      </contrib-group>
      <fpage>532</fpage>
      <lpage>537</lpage>
      <abstract>
        <p>This paper deals with an investigation of specific mechanisms of insight problem solving. We take the functioning of working memory slave system as such mechanisms. In our research we use a dual task method as a cognitive monitor (D. Kahneman) to fixing of microdynamics for study mechanisms of thinking processes. We gathered data showing that modal-specific blocks of working memory are mainly used during insight problem-solving, while solving algorithmic problems uses mainly executive control.</p>
      </abstract>
      <kwd-group>
        <kwd>problem solving</kwd>
        <kwd>working memory</kwd>
        <kwd>insight</kwd>
        <kwd>dual task</kwd>
        <kwd>microdynamics</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>Introduction</title>
      <p>
        To date, the psychology of problem solving did not settle
the question about the legality of allocation of insight
problems in a special category. Accordingly, there are two
alternative positions. Participants of the first approach
        <xref ref-type="bibr" rid="ref1 ref10 ref3 ref5 ref8">(Duncker, 1945; Metcalfe, Wiebe, 1987; Seifert., 1995,
Ohlsson, 1992, Knoblich,, 1999 et al)</xref>
        insist on specificity of
the process of insight solution. Another point of view is held
by representatives of non-specific approach, which denies
the specificity of insight problems as related to algorithmic
problems. They believe that any problem can be reduced to
an algorithm
        <xref ref-type="bibr" rid="ref11 ref14 ref7">(Newell, Simon, 1972; Weisberg, Alba, 1981,
MacGregor, Ormerod, Chronicle, 2002 et al)</xref>
        . In cognitive
psychology, in general, and in the theory of insight problem
solving in particular, there are virtually no data to get a clear
idea of the microdynamics of the thought process, including
solutions of insight problems. Typically, studies on this
subject are exploratory, phenomenological, that do not set a
goal to reveal the underlying mechanisms. The existing
experimental studies mostly don’t reveal the current
solution's genesis of both algorithmic and insight problems.
Basically, in the study of the specifics in this case methods
of distraction, pre-intervention (creation of emotional
background, creating the effect of setting, etc.) are used.
        <xref ref-type="bibr" rid="ref15 ref4">(Wen, Butler, Koutstaal, 2013; Lyusin, 2014)</xref>
        . An
alternative is the research carried out in the paradigm of
differential psychology
        <xref ref-type="bibr" rid="ref2">(Hambrick, Engle, 2003)</xref>
        . Available
methodical arsenal can reveal informative, structural
specificity of insight processes, but has significant
limitations at revealing the dynamics of insight process.
Classical methods of psychology of thinking, such as the the
analysis of thinking aloud protocols (developed by K.
Duncker) and analysis of sections of representations do not
answer this question (about the microdynamics of thought
process) because:
 They have an impact on the process of decision by
interfering with him, distorting his move.
 As a rule, they are based on the verbal report, and
include analysis only conscious components of
thought process. Thus, there is a significant
reduction basically to the phenomenological piece
of the process under consideration.
 They have a very low "sampling rate", while the
process of solutions (especially insight solutions) is
often minimized and meaningful phases of
solutions can take micro intervals (thus only rough
analysis of the dynamics is possible, which is
insufficient for reveal the mechanisms of insight
solutions)
      </p>
      <p>
        One more method is the analysis of movements on
decision tree, used in the works of A. Newell and H. Simon
        <xref ref-type="bibr" rid="ref7">(Newell, Simon, 1972)</xref>
        . The analysis of movements on the
decision tree, in turn, is imposed interpretive by the scheme
priori: it is assumed that the solution to every problem is a
consistent movement between adjacent representations.
Among the methods that allow to reveal the microdynamics
of the solving process the monitoring method should be
allocated.
      </p>
      <p>
        The monitoring method is based on the D. Kahneman's
uniform resource model and implies the parallel solution of
dual tasks. The monitoring method is based on the D.
Kahneman's common resource model and involves
simultaneous solution of two tasks. According to the
Kahneman's model, different structures require different
amount of attention. In addition, their resource requirements
vary in different time moments. The total amount of mental
effort (resource) that is potentially available for a system of
information processing is limited. In order to test the degree
of attention he used the method of the secondary probe task.
The main idea was that it can be possible to "catch" the
moment of the resource’s depletion when the subject deals
with the main problem (complex) and, paradoxically, cannot
cope with the additional secondary problem (simple). The
difference between total effort and an effort that is invested
in the core activity, D. Kahneman calls the spare capacity.
Spare capacity is reduced with the increasing of an effort
required to perform primary problem. Additional
(secondary) problem can only be solved using spare
capacity. If the primary problem requires more cognitive
effort, the spare capacity is reduced and the productivity of
the secondary task solution is reduced by the same amount,
and vice versa. Consequently, the change of productivity of
the secondary task reflects the change in the degree of
mental effort that is invested into primary problem.
Considering attention as a limited resource of mental effort
was further developed in theoretical and applied
investigations. Thus, D. Navon and D.Gopher
        <xref ref-type="bibr" rid="ref6">(Navon,
Gopher, 1979)</xref>
        proposed a model of integrated resource
information processing, i.e, plurality and specificity of
human's energy resources. The degree of interference
between the tasks depends on how similar the combination
of resources is required to complete each of them. Thus, the
theory of resource’s limitations formed the basis of the dual
task paradigm, and this type of the method may be used for
dynamics description.
      </p>
    </sec>
    <sec id="sec-2">
      <title>Method and experimental design</title>
      <p>The dynamics of the resource loading on the main task is
determined by the productivity of the performance of the
secondary task. The primary is a thinking task (problem)
and a tempo task (choice of two alternatives) performed in
parallel. The reaction time and a number of errors in the
implementation of the second task are fixed. The dynamics
of the performance quality serves as a marker of the loading
of working memory by operations which are carried out in
the main problem. The secondary task must satisfy a
number of requirements:
a) the equal complexity,
b) the same procedure of the presentation,
c) the dichotomous choice,
d) the equal probability of alternatives (50/50).</p>
      <p>Decreasing productivity at a given time moment indicates
that currently the resource is used by the primary task. The
main problem's leading representation format (insight /
algorithmic) was varied: visual or text. Similarly the type of
the probe task was varied. It was required to determine the
type of the angle (obtuse - acute) - visual format, or to
determine the type of the syllable (open - closed) - text
format. It is assumed that the coincidence of the format of
the probe task and the main task creates the competition for
a resource and affects the dynamics of the probe-task. To
describe the dynamics and results unification the time to
solve each of the problems was divided into ten equal time
periods. This made it possible to unify the different time
solving problems of different problems in our experimental
trial.</p>
      <p>The problem was the fact that the subject has to correct
the incorrect mathematical statement by moving one match
and parallel to determine the type of syllable. After the
participant has identified the first syllable by pressing the
corresponding key, the following syllable was presented. So
until then, until the problem is resolved. In this case, we see
different formats of leading representation of tasks. There
are visual algorithmic problem and the textual probe task.</p>
      <p>And at this figure, we can see the same format leading
representation of tasks. There are visual algorithmic
problem and the visual probe task. It’s assumed that in this
case cognitive load is higher and the execution of activity is
more difficult.
The Stimulus material was prepared using PsychoPy - an
open-source application to allow the presentation of stimuli
and collection of data for a wide range of neuroscience,
psychology and psychophysics experiments. It’s a free,
powerful alternative to Presentation or e-Prime, written in
Python (Peirce,2007)</p>
    </sec>
    <sec id="sec-3">
      <title>Hypotheses:</title>
      <p>The hypotheses are:
 There is a specificity of insight solution process
regarding algorithmic solution;
 There is a domain specificity of information
processing in the process of insight problem
solving: the nature of the insight solution's
dynamics can be reflected in the dynamics of the
operation of slave systems of working memory.</p>
      <sec id="sec-3-1">
        <title>The independent variables are:</title>
        <p>1) the type of problem (insight / algorithmic)
2) the leading representation's format of the main thinking
problem (visual / text)
3) the representation's format of probe task (visual / text)
The dependent variable is the productivity of the probe
task (reaction time)</p>
        <p>So, the subject of this study is specific information
processing in insight problem solving
Participants. 58 people participated in total.
(Average age is 24 years, from 18 to 56, 36 male and
22 femail. SD = 6). They were asked to solve 8
problems, but first they performed two training tasks.</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>Results</title>
      <p>1.</p>
      <sec id="sec-4-1">
        <title>The Role of the Central Executive in Solving</title>
      </sec>
      <sec id="sec-4-2">
        <title>Problems of Various Types.</title>
        <p>Investigation of the role of the central executive in
solving insight and algorithmic problems was carried out by
comparing the data in the performance of all tasks without
focus on its representation format. An important fact is the
reproducibility of the results. The graph below shows the
results of two experiments performed in a uniform
methodological paradigm.</p>
        <p>There is the graph of reproducibility in two experiments.
The results of the first experiment are shown in Figure 2.
There is a significant dynamics in insight solving problems
and its absence in algorithmic problem solving (Alg: F (9,
149)=2.3, p=.02; η =.12. Ins: F (9, 200)=1.7, p=.09; η =.07)</p>
        <p>Similar results were obtained in our experiment (Figure 2).
But in our trial all results are significant (Alg: F (9,
1479)=3.62, p&lt;.001; η =.06. Ins: F (9, 1479)=10.12, p&lt;.001;
η =.02) (Figure 3).</p>
        <p>We can observe that the data structure is reproduced. The
greater complexity of the task in our series (more reaction
time) is explained by more complexity of the probe-task
(assignment to one of the two categories of 24 stimuli,
whereas in the cited work the incentives were only two). We
found the presence of the dynamics of working memory's
loading in solving algorithmic problems. The expressed
dynamics is manifested in the presence of a "hump" near the
end of the solution. High productivity decreases on the steps
of low-cost operations: the reading of the conditions and the
voicing of the answer. Probably, the decrease in
productivity near the end of the solution is connected with
the implementation of combinatorial operations.</p>
      </sec>
      <sec id="sec-4-3">
        <title>2. The Role of Domain Specificity Units of Working</title>
      </sec>
      <sec id="sec-4-4">
        <title>Memory in Solving Problems of Various Types.</title>
        <p>Also, one of the results of the above-cited studies
(Korovkin, Vladimirov, Savinova, 2012) was the lack of a
dynamics on the insight problem solving. As a possible
reason was the suggestion that manipulations with a
representation are important in insight problem solving and
domain specific units of working memory are utilized rather
than central executive. The purpose of this series was to
investigate the loading of slave modal specific systems of
working memory as a possible locus of information
processing in the insight solutions. Separately for insight
and algorithmic problems let us consider the data on the
average rate performance (average reaction time) of the
probe-task in conditions when its format of representation
matches the format of the thinking problem and in
conditions of the discrepancy between these formats.</p>
        <p>There is a expressed cross effect (F (1, 1527) =5.96,
p=.01; η=.003). When there is coincidence of the leading
type of the representation of the main tasks and the
probetask in the solution of insight problems then we observe a
significantly lower pace of implementation of the secondary
task (probe-task). Especially pronounced effect is for visual
representation. A different picture is observed in algorithmic
problems.</p>
        <p>As can be seen from the graph in the algorithmic type of
tasks the cross effect (F (1, 1493) =.01, p=.9; η&lt;.001) is not
expressed. Probably, these findings can be explained by the
fact that in solving insight problems more important is to
manipulate with the initial representation of the problem,
especially for the "visual" problems where the spatial
characteristics and moving into the field of the problem are
important because of high uncertainty of problem space. In
the type of algorithmic problems, apparently, the central
executive is more important because the main resource
burden falls on a phased program switch solutions that do
not require taking into account the modal specifics, but it's
rather more complicated switching between tasks of
different modalities.</p>
        <p>Summarizing, the data show that slave systems of
working memory are less important for algorithmic
problems. Central executive plays the main role and allows
to keep the algorithm of solutions.</p>
        <p>
          Accordingly, the model designed by H.Simon and
A.
          <xref ref-type="bibr" rid="ref7">Newell (1972)</xref>
          - the model of problem space, which
describes the solution process as a successive movement on
the graph of possible intermediate states between the
condition and purpose most adequately describes the
process of algorithmic problems. Slave systems are loaded
harder in the process of solving the insight problem. In this
case, a subsystem of the same representation's format of the
basic problem is maximally loaded. Most clearly this fact is
expressed for the spatial type of representation. The data
allow us to assume that when a subject solves insight
problems, he manipulates with his own representation by
searching elements and their correlations. Probably, this
process corresponds to the model of problem’s field
proposed by Karl Duncker and has quasi-spatial structure.
        </p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>Conclusions:</title>
      <p>1. A consecutive movement on the decision tree underlies
the solution in the course of solving algorithmic problems.
A significant role in this process is played by the central
executive. For insight problems such process is not
characteristic.
2. A non-directional movement in a field of the problem
(obviously, it's a spatial or quasi-spatial structure) underlies
the solution in the process of insight solving problems.</p>
    </sec>
    <sec id="sec-6">
      <title>Acknowledgments</title>
      <p>This work is supported by Russian Foundation for Basic
Research (grant 15-06-07899a) and The Mikhai
Prokhorov Foundation (Karamzin grant program 2015)</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          <string-name>
            <surname>Duncker</surname>
            ,
            <given-names>K.</given-names>
          </string-name>
          (
          <year>1945</year>
          ).
          <article-title>On problem-solving</article-title>
          .
          <source>Psychological Monographs</source>
          ,
          <volume>58</volume>
          (
          <issue>5</issue>
          )
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          <string-name>
            <given-names>Hambrick D.</given-names>
            ,
            <surname>Engle</surname>
          </string-name>
          <string-name>
            <surname>R.</surname>
          </string-name>
          (
          <year>2003</year>
          )
          <article-title>The Role of Working Memory in Problem Solving .</article-title>
          . Davidson J.,
          <string-name>
            <surname>Sternberg</surname>
            <given-names>R</given-names>
          </string-name>
          . (Eds.).
          <article-title>The Psychology of Problem Solving</article-title>
          . NY:Cambridge University. 176-
          <fpage>207</fpage>
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          <string-name>
            <surname>Knoblich</surname>
            ,
            <given-names>G.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Ohlsson</surname>
            ,
            <given-names>S.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Haider</surname>
            ,
            <given-names>H.</given-names>
          </string-name>
          , &amp;
          <string-name>
            <surname>Rhenius</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          (
          <year>1999</year>
          ).
          <article-title>Constraint relaxation and chunk decomposition in insight problem solving</article-title>
          .
          <source>Journal of Experimental Psychology: Learning, Memory, and Cognition</source>
          ,
          <volume>25</volume>
          (
          <issue>6</issue>
          ),
          <fpage>1534</fpage>
          -
          <lpage>1555</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          <string-name>
            <surname>Lyusin D.V</surname>
          </string-name>
          (
          <year>2014</year>
          ).
          <article-title>The influence of emotion on attention: an analysis of current research. Cognitive psychology: the phenomenon and problems</article-title>
          . Moscow: Lenand Publ,. .
          <fpage>146</fpage>
          -
          <lpage>160</lpage>
          . (In Russian)
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          <string-name>
            <given-names>Metcalfe J.</given-names>
            ,
            <surname>Wiebe</surname>
          </string-name>
          <string-name>
            <surname>D.</surname>
          </string-name>
          (
          <year>1987</year>
          )
          <article-title>Intuition in insight and noninsight problem solving</article-title>
          .
          <source>Memory &amp; Cognition</source>
          , vol.
          <volume>15</volume>
          , no.
          <issue>3</issue>
          ,
          <fpage>238</fpage>
          -
          <lpage>246</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          <string-name>
            <surname>Navon</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          ;
          <string-name>
            <surname>Gopher</surname>
            ,
            <given-names>D.</given-names>
          </string-name>
          (
          <year>1979</year>
          ).
          <article-title>On the economy of the human-processing system</article-title>
          .
          <source>Psychological Review</source>
          , Vol
          <volume>86</volume>
          (
          <issue>3</issue>
          ),.
          <fpage>214</fpage>
          -
          <lpage>255</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          <string-name>
            <given-names>Newell A.</given-names>
            ,
            <surname>Simon</surname>
          </string-name>
          <string-name>
            <surname>H.A.</surname>
          </string-name>
          (
          <year>1972</year>
          )
          <article-title>Human problem solving</article-title>
          .
          <source>Englewood Cliffs</source>
          , NJ: Prentice-Hall.
          <volume>920</volume>
          p.
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          <string-name>
            <surname>Ohlsson S.</surname>
          </string-name>
          (
          <year>1992</year>
          )
          <article-title>Information processing explanations of insight and related phenomena</article-title>
          . In M. Keane,
          <string-name>
            <surname>K.</surname>
          </string-name>
          Gilhooly (Eds.),
          <article-title>Advances in the psychology of thinking</article-title>
          . Vol.
          <volume>1</volume>
          . London, OK: Harvester Wheatsheaf.
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          <string-name>
            <surname>Peirce</surname>
            ,
            <given-names>JW</given-names>
          </string-name>
          (
          <year>2007</year>
          )
          <article-title>PsychoPy - Psychophysics software in Python</article-title>
          .
          <source>J Neurosci Methods</source>
          ,
          <volume>162</volume>
          (
          <issue>1-2</issue>
          ):
          <fpage>8</fpage>
          -
          <lpage>13</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref10">
        <mixed-citation>
          <string-name>
            <given-names>Seifert C.M.</given-names>
            , Meyer D.E.,
            <surname>Davidson</surname>
          </string-name>
          <string-name>
            <given-names>N.</given-names>
            ,
            <surname>Patalano</surname>
          </string-name>
          <string-name>
            <given-names>A.L.</given-names>
            , &amp;
            <surname>Yaniv</surname>
          </string-name>
          <string-name>
            <surname>I.</surname>
          </string-name>
          (
          <year>1995</year>
          )
          <article-title>Demystification of cognitive insight: Opportunistic assimilation and the prepared mind perspective</article-title>
          . Sternberg R.J.,
          <string-name>
            <surname>Davidson</surname>
            <given-names>J.E. (Eds.).</given-names>
          </string-name>
          <article-title>The nature of insight</article-title>
          . NY: Cambridge University Press,..
          <fpage>65</fpage>
          -
          <lpage>124</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref11">
        <mixed-citation>
          <string-name>
            <given-names>Thomas C.</given-names>
            <surname>Ormerod James N. MacGregor Edward P. Chronicle.</surname>
          </string-name>
          (
          <year>2002</year>
          )
          <article-title>Dynamics and Constraints in Insight Problem Solving</article-title>
          .
          <source>Journal of Experimental Psychology, Learning, Memory, and Cognition</source>
          , Vol.
          <volume>28</volume>
          , No.
          <volume>4</volume>
          , .
          <fpage>791</fpage>
          -
          <lpage>799</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref12">
        <mixed-citation>
          <string-name>
            <surname>Vladimirov</surname>
            <given-names>I.Yu.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Korovkin</surname>
            <given-names>S.Yu.</given-names>
          </string-name>
          (
          <year>2014</year>
          )
          <article-title>Working memory as the thinking process utility system. Cognitive psychology: the phenomenon and problems</article-title>
          . Moscow.: Lenand Publ .
          <fpage>8</fpage>
          -
          <lpage>21</lpage>
          .(In Russian)
        </mixed-citation>
      </ref>
      <ref id="ref13">
        <mixed-citation>
          <string-name>
            <surname>Vladimirov</surname>
            <given-names>I.Yu.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Korovkin</surname>
            <given-names>S.Yu.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Chistopol'</surname>
            skaya
            <given-names>A.V.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Savinova</surname>
            <given-names>A.D.</given-names>
          </string-name>
          (
          <year>2013</year>
          )
          <article-title>Executive control load monitoring as a method of the thinking process microdynamics registration. Psychology of cognitive processes</article-title>
          . Smolensk: Universum Publ,. pp.
          <fpage>18</fpage>
          -
          <lpage>22</lpage>
          . (In Russian)
        </mixed-citation>
      </ref>
      <ref id="ref14">
        <mixed-citation>
          <string-name>
            <given-names>Weisberg R.W.</given-names>
            ,
            <surname>Alba</surname>
          </string-name>
          <string-name>
            <surname>J.W</surname>
          </string-name>
          (
          <year>1981</year>
          ).
          <article-title>An examination of the alleged role of “fixation” in the solution of “insight” problems</article-title>
          . Journal of Experimental Psychology: General,, vol.
          <volume>110</volume>
          ,
          <fpage>169</fpage>
          -
          <lpage>192</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref15">
        <mixed-citation>
          <string-name>
            <surname>Wen</surname>
            ,
            <given-names>M.C.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Butler</surname>
            ,
            <given-names>L.T.</given-names>
          </string-name>
          , &amp;
          <string-name>
            <surname>Koutstaal</surname>
            ,
            <given-names>W.</given-names>
          </string-name>
          (
          <year>2013</year>
          ).
          <article-title>Improving insight and non insight problem solving with brief interventions</article-title>
          .
          <source>British Journal of Psychology</source>
          ,
          <volume>104</volume>
          (
          <issue>1</issue>
          ),
          <fpage>97</fpage>
          -
          <lpage>118</lpage>
          .
        </mixed-citation>
      </ref>
      <ref id="ref16">
        <mixed-citation>
          <string-name>
            <surname>Wiley</surname>
            ,
            <given-names>J.</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Jarosz</surname>
            ,
            <given-names>A.F.</given-names>
          </string-name>
          (
          <year>2012</year>
          )
          <article-title>How working memory capacity affects problem solving</article-title>
          .
          <source>Psychology of Learning and Motivation</source>
          , vol.
          <volume>56</volume>
          ,
          <fpage>185</fpage>
          -
          <lpage>227</lpage>
          .
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>