SMITH, L. Split Extensions of Hopf Algebras and Semi-Tensor Products. MATHEMATICA SCANDINAVICA, [S. l.], v. 26, p. 17–41, 1970. DOI: 10.7146/math.scand.a-10963. Disponível em: https://www.mscand.dk/article/view/10963. Acesso em: 9 may. 2024.