{% endfor %}
+{% with extra_info=book.get_extra_info_json %}
{% if extra_info.source_url %}
<div class="white-box">
<a href="{{ extra_info.source_url }}">{% trans "Source" %}</a> {% trans "of the book" %}
<div class="white-box">
<a href="{% url 'poem_from_book' book.slug %}">{% trans "Mix this book" %}</a>
</div>
+{% endwith %}
{% endblock %}