<div class=“book-summary” id=“bookSummary”>

<nav role="navigation">
  <ul class="summary">
    <li class="chapter {% if page.book.index.url == page.url -%}active{% endif -%}">
      <a href="{{ page.book.url | relative_url }}" class="custom-link">{{ page.book.title }}</a>
    </li>
    <li class="divider"></li>
    {%- for part in page.book.parts -%}
    <li class="chapter {% if part.url == page.url -%}active{% endif -%}">
      {%- if part.url -%}
      <a href="{{ part.url | relative_url }}">{{ part.title }}</a>
      {%- else -%}
      <span>{{ part.title }}</span>
      {%- endif -%}

      {%- if part.parts.size > 0 -%}
      <ul class="articles">
        {%- for part in part.parts -%}

        <li class="chapter {% if part.url == page.url -%}active{% endif -%}">
          <a href="{{ part.url | relative_url }}">{{ part.title }}</a>
        </li>
        {%- endfor -%}
      </ul>
      {%- endif -%}
    </li>
    {%- endfor -%}
  </ul>
</nav>

</div>