diff --git a/doc/userguide.html b/doc/userguide.html
index f1860480..059b4eaf 100755
--- a/doc/userguide.html
+++ b/doc/userguide.html
@@ -159,6 +159,8 @@ For the quality of the information committed to the logbook, you need understand
 <p>
 <li>a nice touch : URLs in attributes (http://..., ftp://..., mailto:...) are automatically converted to links.
 <p>
+<li>in addition to the above URLs, one can enter a tag <b>elog:&lt;id&gt;</b> which references another logbook entry. The tag <b>elog:&lt;logbook&gt;/&lt;id&gt;</b> references a message in another logbook on the same server.
+<p>
 <li>the Text multi-line field, if present, may be pre-filled with a template if entries need to have a common, consistent format across the logbook (especially for HTML). There may also be a comment inserted before it to explain local rules and conventions, upload rules, etc.
 <p>
 <li>check the "<I>Submit as HTML</I>" box if the entry contains HTML markup.