A normal criterion about two families of meromorphic functions concerning shared values

In this paper, we mainly discuss the normality of two families of functions concerning shared values and proved: Let F and G be two families of functions meromorphic on a domain D . ., a 1, a 2, a 3, a 4 be four distinct finite complex numbers. If G is normal, and for every f . F, there exists g . G such that f(z) and g(z) share the values a 1, a 2, a 3, a 4, then F is normal on D.