Institute of Applied Mathematics, South China Agricultural University, Guangzhou 510642, P. R. China
Abstract:
Let{fn} be a sequence of functions meromorphic in a domain D, let {hn} be a sequence of holomorphic functions in D, such that hn(z)h(z), where h(z)≠ 0 is holomorphic in D, and let k be a positive integer. If for each n ∈ N+, fn(z)≠0 and fn(k)(z)-hn(z) has at most k distinct zeros (ignoring multiplicity) in D, then {fn} is normal in D.