Chabanyuk, Y. M. “Stability of a Dynamical System With Semi-Markov Switchings under Conditions of Diffusion Approximation”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 59, no. 9, Sept. 2007, pp. 1290–1296, https://umj.imath.kiev.ua/index.php/umj/article/view/3388.