Ptashnik, B.I. and Symotyuk, M.M. (2003) “Multipoint Problem for Nonisotropic Partial Differential Equations with Constant Coefficients”, Ukrains’kyi Matematychnyi Zhurnal, 55(2), pp. 241–254. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3902 (Accessed: 5 December 2025).