Changes by: Xin Yu (xiny at cs.caltech.edu)
Date: 2002-04-08 22:59:41 -0700 (Mon, 08 Apr 2002)
Revision: 3570
Log message:
Updated the definition of subgroups and cyclic subgroups utilizing
group_bvd. They look much cleaner now.
Also updated related rules and their proofs.