(=> (= (Ref.Volume ?Ref) ?Number)
(Or (Book-Reference ?Ref)
(Book-Section-Reference ?Ref)
(Article-Reference ?Ref)))
(=> (Ref.Issue $X $Y) (Article-Reference $X))
(=> (= (Ref.Pages ?Ref) ?Page-Range)
(Or (Book-Section-Reference ?Ref)
(Article-Reference ?Ref)
(Proceedings-Paper-Reference ?Ref)))
(=> (= (Ref.Month ?Ref) ?Month)
(Or (Article-Reference ?Ref) (Technical-Report ?Ref)))
(=> (= (Ref.Day ?Ref) ?Day)
(Or (Article-Reference ?Ref)
(Personal-Communication-Reference ?Ref)))
(Subclass-Partition Publication-Reference
(Setof Book-Reference
Book-Section-Reference
Article-Reference
Proceedings-Paper-Reference
Thesis-Reference
Technical-Report-Reference
Misc-Publication-Reference))