Valeyev, K.G. and Dzhalladova, I.A. (2003) “Derivation of Moment Equations for Solutions of a System of Nonlinear Difference Equations Dependent on a Semi-Markov Process”, Ukrains’kyi Matematychnyi Zhurnal, 55(6), pp. 858–864. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3960 (Accessed: 6 December 2025).