Fečkan, M., and M. Pospíšil. “On Equations With Generalized Periodic Right-Hand Side”. Ukrains’kyi Matematychnyi Zhurnal 70, no. 2 (February 25, 2018): 255-279. Accessed April 25, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1555.