Moskal'tsova, N. V., and V. M. Shurenkov. 1993. “Central Limit Theorem for Centered Frequencies of a Countable Ergodic Markov Chain”.
Ukrains’kyi Matematychnyi Zhurnal
45 (12): 1713–1715.
https://umj.imath.kiev.ua/index.php/umj/article/view/5982
.