Normality Of Differential Polynomials On Meromorphic Function

Let F be a family of meromorphic functions on the plane domain D,P(z,f,f') = P₀(z, f)(f')^m+P₁(z, f)(f')^m-1+....+P_m(z,f) is differential polynomial about z,f,f', deg_zP_j(z, f)= C_j(f) is order of P_j(z,f) about z. a₁,a₂,a₃∈C are three distinct numbers. S ={a₁,a₂,a₃}. For any f∈F there exitsδ>0, such that if f(z)∈S then |P₀(z,f)|>δ.If for every f∈F , f and P(z, f,f') share the set S, then F is normal on D .