Two perturbation results on the linear differential function f″ ＋ Π（z）A（z）f = 0 are obtained, where Π（z） and A（z） are periodic entire functions with period 2πi and σe（Π） 〈 σe（A）.
基金Supported by the College's Ph.D Foundation of China(20050574002)the Natural Science Foundation of Guangdong Province(06025059)
文摘Two perturbation results on the linear differential function f″ ＋ Π（z）A（z）f = 0 are obtained, where Π（z） and A（z） are periodic entire functions with period 2πi and σe（Π） 〈 σe（A）.
