“…Recently, some papers are devoting to improve Theorem C, the constant a can be replaced by a nonzero polynomial [12] or by a small function a(z) [15]. In addition, [13,14,18,27] are devoting to the cases of meromorphic function f or more general difference products. In the following, without special stated, we assume that c is a nonzero constant, n, m, k, s, t are positive integers, a(z) is a nonzero small function with respect to f (z).…”