Barbu, V. S. ., J. . Bulla, and A. . Maruotti. “ESTIMATION OF THE STATIONARY DISTRIBUTION OF A SEMI-MARKOV CHAIN”. Journal of Reliability and Statistical Studies, vol. 5, Jan. 2012, pp. 15-26, https://journals.riverpublishers.com/index.php/JRSS/article/view/21949.