Update archive-single.html

Author: staeiou

_includes/archive-single.html

@@ -51,7 +51,7 @@ <h2 class="archive__item-title" itemprop="headline">
     {% endif %}
 
     {% if post.citation %}
-      <p>Recommended citation: {{ post.citation }}</p>
+      <p>Recommended citation: {{ post.citation }} {% if post.paperurl %} {{<a href=" {{ post.paperurl }} "><u>{{ post.paperurl }}</u></a>}} {% endif %}</p>
     {% endif %}
 
   </article>