Let n be an integer not less than 5, and let a and b be complex numbers with
. Let f be a family of functions meromorphic in a domain D such that for each f in F,
has no solutions in D. Then F is a normal family in D. Some lemmas of Gu Yongxing
) [Sci. Sin. 21, 431-445 (1978)] are used in the proof. D. Drasin
[Acta Math. 122, 231-263 (1969; Zbl 0176.028
)] proved the analogous theorem for analytic functions in D.