{% load thumbnail %}
<h2 class="header">{{ entity.label }}</h2>

<div class="l-book_list">
{% for ref in entity.reference_set.all %}
  <a href='/katalog/lektura/{{ ref.book.slug }}.html#{{ ref.first_section }}' target="_blank">
    {% thumbnail ref.book.cover_clean '150x150' as th %}
    <img src="{{ th.url }}" alt="{{ ref.book.pretty_title }}" title="{{ ref.book.pretty_title }}">
    {% endthumbnail %}
  </a>
{% endfor %}