SokilB. I. (1994) “Construction of one-frequency solutions of boundary-value problems for a nonautonomous wave equation”, Ukrains’kyi Matematychnyi Zhurnal, 46(9), pp. 1275–1279. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5646 (Accessed: 24November2024).