Abdelkader Boucherif, Eduardo García-Río, Juan J. Nieto, "Periodic solutions of quasi-differential equations", International Journal of Stochastic Analysis, vol. 9, Article ID 241932, 10 pages, 1996. https://doi.org/10.1155/S1048953396000020
Periodic solutions of quasi-differential equations
Existence principles and theorems are established for the nonlinear problem where is a quasi-differential operator and is a Carathéodory function. We prove a maximum principle for the operator and then we show the validity of the upper and lower solution method as well as the monotone iterative technique.
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