Romanyuk, A. S., & Samoilenko, A. M. (2008). Bogolyubov Readings-2008. International Conference "Differential Equations, Theory of Functions and Applications" (on the occasion of the 70th anniversary of academician AM Samoilenko). Ukrains’kyi Matematychnyi Zhurnal, 60(12), 1722. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/3285