SOKHATS’KYI, F. M. Abstract Characteristic of the Class of Unitary Positional Algebras of Operations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 54, n. 7, p. 961–968, 2002. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4132. Acesso em: 6 dec. 2025.