ShchegolevS. A. (1999). A resonance case of the existence of solutions of a quasilinear second-order differential system, which are represented by Fourier series with slowly varying parameters. Ukrains’kyi Matematychnyi Zhurnal, 51(2), 285–288. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/4612