Existence of almost periodic weak type solutions for the conservative forced pendulum equation
This paper gives sufficient conditions for the existence of almost periodic solutions to the conservative forced pendulum equation \(x''+ bx+ A\sin x= e\). Earlier, this was solved for the case \(b= 0\) and \(0< A< 2\pi/T\) (see, e.g., \textit{A. Castro} [Differential Equations, Proc. 8th Fall Conf., Okla. State Univ. 1979, 149-160 (1980; Zbl 0569.34039)]).
scientific article; zbMATH DE number 838715