Vasylyshyn, P.B. and Ptashnik, B.I. (1998) “A multipoint problem for partial integro-differential equations”, Ukrains’kyi Matematychnyi Zhurnal, 50(9), pp. 1155–1168. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/4832 (Accessed: 6 December 2025).