Normal Criterions Concerning Shared Values

It's an important topic in the theory of normal family that considering the normal family with shared values. This paper studies the normal families when they share some values. Through the analysis, the author obtains some normality criteria. In the begin of this paper, the theory of Nevanlinna is introduced because of its important role in the study of normal families. Then, the author discusses the value distribution of differential polynomial fⁿf^k.