[1] Cabada A. The method of lower and upper solutions for second, third, fourth and higher order boundary value problem. J Math Anal Appl, 1994, 185: 302--320
[2] Cabada A, Lions S. Maximum principles for fourth and sixth order periodic boundary problems. Nonlinear Anal TMA, 1997, 29: 1161--1171
[3] Jiang D Q. On the existence of positive solutions to second order periodic BVPs. Acta Math Scientia, 1998, 18B: 31--35
[4] Rachunkov\'a I, Tvrd\'y M, Vrkoc I. Existence of nonnegative and nonpositive solutions for second order periodic boundary value problems. J Differential Equations, 2001, 176: 445--469
[5] Erbe L H, Mathsen R M. Positive solutions for singular nonlinear boundary value problems. Nonlinear Anal TMA, 2001, 46: 979--986
[6] Torres P J. Existence of one-signed periodic solutions of some second-order differential equations via a Krasnoselskii fixed point theorem. J Differential Equations, 2003, 190: 643--662
[7] Li Y X. Positive solutions of fourth-order periodic boundary value problems. Nonlinear Anal TMA, 2003, 54: 1069--1078
[8] Yao Q L. Existence, multiplicity and infinite solvability of positive solutions to a nonlinear fourth-order periodic boundary value problem. Nonlinear Anal TMA, 2005, 63: 237--246
[9] Yao Q L. Positive solutions of nonlinear second-order periodic boundary value problems. Appl Math Letters, 2007, 20: 583--590
[10] 姚庆六. 一类奇异二阶边值问题的正周期解. 数学学报(中文版), 2007, 50: 1357--1364
[11] 姚庆六. 变系数非线性二阶周期边值问题的正解. 应用数学学报(中文版), 2008, 34: 564--573
[12] Omari P, Trombetta M. Remarks on the lower and upper solutions method for second and third order periodic boundary value problems. Appl Math \& Comput, 1992, 50: 1--21
[13] Cabada A. The method of lower and upper solutions for third order periodic boundary value problems. J Math Anal Appl, 1995, 195: 568--589
[14] Kong L B, Wang S S, Wang J Y. Positive solutions of a singular third-order periodic boundary value problem. J Comput Appl Math, 2001, 132: 247--253
[15] Sun J X, Liu Y S. Multiple positive solutions of singular third-order periodic boundary value problem. Acta Math Scientia, 2005, 25B: 81--88
[16] 姚庆六. 非线性三阶边值问题的正周期解. 山东大学学报(理学版), 2009, 44(2): 14--18
[17] Yao Q L. Positive solutions of nonlinear elastic beam equation rigidly fastened on the left and simply supported on the right. Nonlinear
Anal TMA, 2008, 69: 1570--1580
[18] Guo D J, Lakshmikantham V. Nonlinear Problems in Abstract Cone. Boston: Academic Press, 1988
|