Karnaukh, E. V. “Behavior of an Almost Semicontinuous Poisson Process on a Markov Chain Upon Attainment of a Level”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 62, no. 1, Jan. 2010, pp. 81–89, https://umj.imath.kiev.ua/index.php/umj/article/view/2844.