Klymchuk, S. O., O. P. Makarchuk, and M. V. Pratsiovytyi. “Frequency of a Digit in the Representation of a Number and the Asymptotic Mean Value of the Digits”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 66, no. 3, Mar. 2014, pp. 302–310, https://umj.imath.kiev.ua/index.php/umj/article/view/2133.