Normality Criteria of Meromorphic Functions

In this paper,we consider normality criteria for a family of meromorphic functions concerning shared values.Let F be a family of meromorphic functions defined in a domain D,m,n,k and d be four positive integers satisfying m≥ n + 2and d ≥（k+1）/（m-n-1）,and a（≠ 0）,6 be two finite constants.Suppose that every f ∈ F has all its zeros and poles of multiplicity at least k and d,respectively.If（fn）（k）—afm and（gn）（k）- agm share the value b for every pair of functions（/,g） of J',then IF is normal in D.Our results improve the related theorems of Schwick（Schwick W.Normality criteria for families of meromorphic function.J.Anal.Math.,1989,52:241-289）,Li and Gu（Li Y T,Gu Y X.On normal families of meromorphic functions.J.Math.Anal.Appl.,2009,354:421-425）.更多还原