diff --git a/theme/templates/includes/book/summary.html b/theme/templates/includes/book/summary.html
index b4859fce0..697cce87c 100644
--- a/theme/templates/includes/book/summary.html
+++ b/theme/templates/includes/book/summary.html
@@ -1,3 +1,22 @@
+{% macro articles(_articles) %}
+    {% for item in _articles %}
+        <li class="chapter {% if item._path == _input %}active{% endif %}" data-level="{{ item.level }}" {% if item.path %}data-path="{{ item.path|mdLink }}"{% endif %}>
+            {% if item.path %}
+            <a href="{{ basePath }}/{{ item.path|mdLink }}">
+                <i class="fa fa-check"></i> <b>{{ item.level }}.</b> {{ item.title }}
+            </a>
+            {% else %}
+            <span><b>{{ item.level }}.</b> {{ item.title }}</span>
+            {% endif %}
+            {% if item.articles.length > 0 %}
+            <ul class="articles">
+                {{ articles(item.articles) }}
+            </ul>
+            {% endif %}
+        </li>
+    {% endfor %}
+{% endmacro %}
+
 <div class="book-summary">
     <div class="book-search">
         <input type="text" placeholder="Search" class="form-control" />
@@ -32,32 +51,7 @@
         <li data-level="0" data-path="index.html">
             <a href="{{ basePath }}/"><i class="fa fa-check"></i> Introduction</a>
         </li>
-        {% for item in summary.chapters %}
-            <li class="chapter {% if item._path == _input %}active{% endif %}" data-level="{{ item.level }}" {% if item.path %}data-path="{{ item.path|mdLink }}"{% endif %}>
-                {% if item.path %}
-                <a href="{{ basePath }}/{{ item.path|mdLink }}">
-                    <i class="fa fa-check"></i> <b>{{ item.level }}.</b> {{ item.title }}
-                </a>
-                {% else %}
-                <span><b>{{ item.level }}.</b> {{ item.title }}</span>
-                {% endif %}
-                {% if item.articles.length > 0 %}
-                <ul class="articles">
-                    {% for article in item.articles %}
-                        <li {% if article._path == _input %}class="active"{% endif %} data-level="{{ article.level }}" {% if article.path %}data-path="{{ article.path|mdLink }}"{% endif %}>
-                            {% if article.path %}
-                            <a href="{{ basePath }}/{{ article.path|mdLink }}">
-                                <i class="fa fa-check"></i> <b>{{ article.level }}.</b> {{ article.title }}
-                            </a>
-                            {% else %}
-                            <span><b>{{ article.level }}.</b> {{ article.title }}</span>
-                            {% endif %}
-                        </li>
-                    {% endfor %}
-                </ul>
-                {% endif %}
-            </li>
-        {% endfor %}
+        {{ articles(summary.chapters) }}
 
         {% if options.links.gitbook !== false %}
         <li class="divider"></li>