Changes by: Xin Yu (xiny at cs.caltech.edu)
Date: 2001-09-23 00:25:28 -0700 (Sun, 23 Sep 2001)
Revision: 3404
Log message:
1. Minor changes in czf_itt_group;
2. Define subgroup and abelian group;
3. Define cyclic subgroup and cyclic group. However, there are
problems with the proofs in czf_itt_cyclic_subgroup.