Feller, M.N., Belopolskaya, Y.I. and Albeverio, S. (2005) “Riquier problem for nonlinear elliptic equations with Lévy Laplacians”, Methods of Functional Analysis and Topology, 11(1), pp. 1–9. Available at: https://zen.imath.kiev.ua/index.php/mfat/article/view/261 (Accessed: 16 December 2025).