Goi, T.P. and Ptashnik, B.I. (1997) “Nonlocal boundary-value problems for systems on linear partial differential equations”, Ukrains’kyi Matematychnyi Zhurnal, 49(11), pp. 1478–1487. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5147 (Accessed: 5 December 2025).