T. I. Nasirova and K. K. Omarova, “Distribution of the lower boundary functional of the step process of semi-Markov random walk with delaying screen at zero”, Ukr. Mat. Zhurn., vol. 59, no. 7, pp. 912–919, Jul. 2007, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3356