Bibliographies

I'm relatively new to Docbook, and would appreciate someone's  
confirming a conclusion I have come to. For my application, I need to  
have keywords and classification numbers in my bibliographic entries.  
The conclusion I've come to is that the only way to do that in  
Docbook is by means of bibliomisc elements, since keywordsets and  
subjectsets are (for some reason) not allowed in biblioentries. Is  
there a better strategy I've overlooked?

  - dam