SMITH, Larry. Split Extensions of Hopf Algebras and Semi-Tensor Products. Mathematica Scandinavica, Berkeley, CA, United States, v. 26, p. 17–41, 1970. DOI: 10.7146/math.scand.a-10963. Disponível em: https://journals.msp.org/mscand/article/view/2364. Acesso em: 25 jul. 2026.