KOCK, A.; KRISTENSEN, L. A Secondary Product Structure in Cohomology Theory. MATHEMATICA SCANDINAVICA, [S. l.], v. 17, p. 113–149, 1965. DOI: 10.7146/math.scand.a-10768. Disponível em: https://www.mscand.dk/article/view/10768. Acesso em: 2 may. 2024.