Moskal’tsovaN. V., and ShurenkovV. M. “On Potentials of Ergodic Markov Chains”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 46, no. 4, Apr. 1994, pp. 446–449, https://umj.imath.kiev.ua/index.php/umj/article/view/5745.