Valeyev, K. G., & Dzhalladova, I. A. (2002). Derivation of Moment Equations for Solutions of a System of Differential Equations Dependent on a Semi-Markov Process.
Ukrains’kyi Matematychnyi Zhurnal,
54(11), 1569-1573.
https://umj.imath.kiev.ua/index.php/umj/article/view/4193