2Hayman W. Meromorphic Function. Oxford: Clarendon Press, 1964.
3Laine I. Nevanlinna Theory and Complex Differential Equations. Berlin: W de Gruyter, 1993.
4Gundersen G, Steinbart M. Subnormal solutions of second order linear differential equations with periodic coefficients. Results in Math, 1994, 25:270-289.
5Wittich H. Subnormale losungen der differentialgleichung w" + p(e^z)w' + q(e^z)w = 0. Nagoya Math J,1967, 30:29-37.
6Chiang Y M, Gao S A. On a problem in complex oscillation theory of periodic second order linear differential equations and some related perturbation results. Ann Acad Sci Fenn Math, 2002, 27:273-290.
7Urabe H, Yang C C. On factorization of entire functions satisfying differential equations. Kodai Math J,1991, 14:123-133.
8Gundersen G. Finite order solutions of second order linear differential equations. Trails Amer Math Soc,1988, 305:415-429.
9Gundersen G. Estimates for the logarithmic derivative of a meromorphic function, plus similar estimates.J London Math Soc, 1988, 37:88-104.
10Chen Z X. On the growth of solutions of a class of higher order diffential equations. Chin Ann of Math,2003, 24B(4): 501-508.
4HAYMAN W K. Meromorphic functions [ M ]. Oxford: Clarendon Press, 1964.
5LAINE I. Nevanlinna theory and complex differential equations[ M]. Berlin: W de Gmyter, 1993.
6GUNDEREN G, STINBART M. Subnormal solutions of second order linear differential equations with periodic co- efficients[J]. Results in Math, 1994, 25:270-289.
7CHEN Zongxuan. Zeros of meromorphic solutions of high- er order linear differential equations[ J]. Analysis, 1994, 14 : 425 - 438.
8Wittich H. Subnormale lostmgen der differentialgleichtmg w^n+p(e^x)w' +q(e^x)w =0 [J]. Nagoya Math J,1967, 30 : 29 -37.
9Huang Zhibo, Xia Xiaohua, Li Qian. Subnormal solutions of second order nonhomogeneous linear periodic differenti-al equations [ J ]. Commun Nonlinea Sci Numer Simulat, 2010,15(4) :881-885.
10Chiang Y M, Gao Shian. On a problem in complex oscilla- tion theory of periodic second order linear differential e- quation and some related perturbation results [ J ]. Ann Acad Sci Fenn Math,2002,27(2) :273-290.
