Sokhats’kyi, F. M. “Abstract Characteristic of the Class of Unitary Positional Algebras of Operations”. Ukrains’kyi Matematychnyi Zhurnal 54, no. 7 (July 25, 2002): 961–968. Accessed December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/4132.