{%- if prev %}
  <li><a href="{{ prev.link|e }}"
         title="{{ _('Previous Chapter: ') + prev.title|striptags }}">{{ "&laquo;"|safe }} {{ prev.title|striptags|truncate(length=16, killwords=True) }}</a></li>
{%- endif %}
{%- if next %}
  <li><a href="{{ next.link|e }}"
         title="{{ _('Next Chapter: ') + next.title|striptags }}">{{ next.title|striptags|truncate(length=16, killwords=True) }} {{ "&raquo;"|safe }}</a></li>
{%- endif %}

{%- if prev %}
  <li class="visible-md visible-lg"><a href="{{ prev.link|e }}"
         title="{{ _('Previous Chapter: ') + prev.title|striptags }}">{{ "&laquo;"|safe }} {{ prev.title|striptags|truncate(length=16, killwords=True) }}</a></li>
{%- endif %}
{%- if next %}
  <li class="visible-md visible-lg"><a href="{{ next.link|e }}"
         title="{{ _('Next Chapter: ') + next.title|striptags }}">{{ next.title|striptags|truncate(length=16, killwords=True) }} {{ "&raquo;"|safe }}</a></li>
{%- endif %}

Change visibility of next links for CSS
Change visibility of next links for CSS
