Normal families of meromorphic functions with multiple zeros

Let F be a family of meromorphic functions defined in a domain D such that for each f ∈ F , all zeros of f ( z ) are of multiplicity at least 3, and all zeros of f ′ ( z ) are of multiplicity at least 2 in D . If for each f ∈ F , f ′ ( z ) − 1 has at most 1 zero in D , ignoring multiplicity, then F is normal in D .