I use elog's built-in ticketing system, and use the auto-generated ticket number to cross-reference with other matters/documents/files.  Much of the documentation for tickets is rather buried away under Subst <attribute> = <string>.

I've not found a way to link from an entry to a set of entries in another thread by their ticket number, particularly across more than one logbook.  [This is possible via their elog entry number, and which logbook it is in].  The former would be usefil to cross-reference an incident which you identify external to the elog system - "Oh, it's another one like [Ticket no] NOV12-001" possibily easier than "Oh it's another one like elog:archive12/67142 ".  Oh, the last bit should be highlighed as a (non-existant) link here, to show my point, nice of the ticket could be as well.

On the plus side, you can arrange the ticket number to show up in the thread display, quick search by ticket number, run different ticket colours (as it were) in different logbooks (i.e. different prefixes).  Just ensure you don't archive the latest entry, as that can lead to duplication of ticket numbers.