gitbook/theme/templates/includes/book/summary.html

<div class="book-summary">
    <ul class="summary">
        <li>
            <a href="{{ githubHost }}{{ githubAuthor }}" target="blank">About the author</a>
        </li>
        <li>
            <a href="{{ githubHost }}{{ githubId }}/issues" target="blank">Questions and Issues</a>
        </li>
        <li>
            <a href="{{ githubHost }}{{ githubId }}/edit/master/{{ _input }}" target="blank">Edit and Contribute</a>
        </li>
        <li class="divider"></li>
        <li data-level="0">
            <a href="{{ basePath }}/"><i class="fa fa-check"></i> Introduction</a>
        </li>
        {% for item in summary.chapters %}
            <li {% if item._path == _input %}class="active"{% endif %} data-level="{{ item.level }}">
                {% 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 %}
                            <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 %}
    </ul>
</div>