roatabo
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طلب من الأخوه الأعزاء
J.W.BEBERNES, R. E. GAINES and K. SCHMITT, Existence of periodic solutions of third and fourth order ordinary differential equations via coincidence degree, Ann. Soc. Sci. Bruxelles ser. I 88 (1974)25-36
L. CESARI , Functional analysis and periodic solutions of nonlinear differential equations, Contributions to Differential Equations 1 (1963)149-187
S. SEDSIWY , On periodic solutions of a certain third-order non-linear differential equation, Ann. Polon. Math. 17 (1965) 147-154
J. T. SCHWARTZ ," Nonlinear Functional analysis", Gordon and Breach , New York , 1969
L. CESARI , Functional analysis and periodic solutions of nonlinear differential equations, Contributions to Differential Equations 1 (1963)149-187
S. SEDSIWY , On periodic solutions of a certain third-order non-linear differential equation, Ann. Polon. Math. 17 (1965) 147-154
J. T. SCHWARTZ ," Nonlinear Functional analysis", Gordon and Breach , New York , 1969
AND MANY THANX FOR EVERY THING
