1. Hayman, W.K. 1967. Research Problems of Function Theory. London: Athlone Press of University of London.
2. Yang, L., and G. Zhang. 1965. Recherches sur la normalit$$\acute{e}$$ des familles de fonctions analytiques $$\grave{a}$$ des valeurs multiples, Un nouveau crit$$\grave{e}$$re et quelques applications. Scientia Sinica Series A 14: 1258–1271.
3. Gu, Y.X. 1978. On normal families of meromorphic functions. Scientia Sinica Series A 4: 373–384.
4. Pang, X.C. 1988. Bloch’s principle and normal criterion. Scientia Sinica Series A 11: 1153–1159.
5. Chen, H.H., and M.L. Fang. 1995. On the value distribution of $$f^nf^{\prime }$$. Science China Series A 38: 789–798.