title_body: looking for an easy way to look up possible values for Dublin Core Metadata Element Set etc I'm looking for an easy way to look up possible values for Dublin Core Metadata Element Set elements and so on.
  For example, a metadata element (sorry if my terminology is wrong here) might be: 
  
  &lt;dc:language&gt;en-US&lt;/dc:language&gt;
  
  
  .  How do I find out if, for example, an accepted alternative value here is en-AU or something else, i.e.:
  
  &lt;dc:language&gt;en-AU&lt;/dc:language&gt;
  
  
  I've looked here: http://wiki.dublincore.org/index.php/User_Guide/Publishing_Metadata#dc:language ( and here http://www.idpf.org/epub/30/spec/epub30-publications.html).
  
  Thanks for any help.
upvoted_answer: Sigil (freeware) will automatically insert the proper metadata entries for epub3 (and epub2) books.
  
  (You'll have to delete the default dc:language en entry. 
  Then click Add Metadata, OK and select the language.)
  
  AFAIK, it supports all metadata entries listed in the epub3 and epub2 specs.