Pratsiovytyi, M. V., S. O. Klymchuk, and O. P. Makarchuk. 2016. “Level Sets of Asymptotic Mean of Digits Function for $4$-Adic Representation of Real Number”. Methods of Functional Analysis and Topology 22 (2): 184-96. https://zen.imath.kiev.ua/index.php/mfat/article/view/635.