  In this paper, we prove some uniqueness results which improve and generalize
several earlier works. Also, we prove a value distribution result concerning
$f^{(k)}$ which provides a partial answer to a question of Fang and Wang [A
note on the conjectures of Hayman, Mues and Gol'dberg, Comp. Methods, Funct.
Theory (2013)13, 533-543].
