NIZHNIK, L. P.; TUROWSKA, L. B. Representations of double commutator by matrix-differential operators. Methods of Functional Analysis and Topology, [S. l.], v. 3, n. 3, p. 75–80, 1997. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/44. Acesso em: 19 dec. 2025.