Last modified: 2011-08-21 11:58:13 UTC
In the index form, a separate subtitle field is needed. See for example http://fr.wikisource.org/wiki/Livre:Burnouf_-_Lotus_de_la_bonne_loi.djvu
Local administrators should be able to add this by editing the Mediawiki namespace. I think the relevant messages are [[:fr:s:MediaWiki:Proofreadpage index attributes]] (for the input form) and [[:fr:s:MediaWiki:Proofreadpage index template]] (for displaying the information). If this is something that all wikis would want it is possible to change the default messages for the ProofreadPage extension. But I think many Wikisources still needs to add this locally to see any change since they have already customised the messages.
It can be changed on MediaWiki:Proofreadpage_index_attributes.