Some Normality Criteria for Families of Meromorphic Functions

Let k be a positive integer and F be a family of meromorphic functions in a domain D such that for each f ∈ F,all poles of f are of multiplicity at least 2,and all zeros of f are of multiplicity at least k + 1.Let a and b be two distinct finite complex numbers.If for each f ∈ F,all zeros of f(k)-a are of multiplicity at least 2,and for each pair of functions f,g ∈ F,f(k) and g(k) share b in D,then F is normal in D.