HÅVERSEN, Sigfred. Stability of pencils of cubic surfaces in $P^3$. Mathematica Scandinavica, Berkeley, CA, United States, v. 84, n. 1, p. 49–61, 1999. DOI: 10.7146/math.scand.a-13932. Disponível em: https://journals.msp.org/mscand/article/view/964. Acesso em: 25 jul. 2026.