Mustafokulov, R. (1996) “Some boundary-value problems for a class of fourth-order differential equations on a graph”, Ukrains’kyi Matematychnyi Zhurnal, 48(4), pp. 476–482. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5312 (Accessed: 5 December 2025).