LAUDAL, O. A.; SLETSJOE, A. Betti numbers of monoid algebras. Applications to 2-dimensional torus imbeddings. MATHEMATICA SCANDINAVICA, [S. l.], v. 56, p. 145–162, 1985. DOI: 10.7146/math.scand.a-12093. Disponível em: https://www.mscand.dk/article/view/12093. Acesso em: 5 may. 2024.