GROUPS OF OPERATORS IN C2 DETERMINED BY SOME COSINE OPERATOR FUNCTIONS IN C2. Balkan Journal of Applied Mathematics and Informatics, [S. l.], v. 3, n. 1, p. pp. 63–72, 2020. Disponível em: https://js.ugd.edu.mk/index.php/bjami/article/view/3517. Acesso em: 3 okt. 2025.