15.Considering the subnormal subgroups,some equivalent conditions for nilpotency of finite groups are given and a sufficient condition for nilpotency of finite groups is obtained.
16.This paper retrospects briefly the history of the discovery of Parity Nonconservation, analyses some questions on the Lee-Yang's Argument, and also makes comments on it.
17.The kings prblems in semicomplete digraphs without vertices whose in-degree are zero and locally semicomplete digraph under some conditions are discussed chiefly in the paper.