KRISTENSEN, Leif. On a Cartan Formula for Secondary Cohomology Operations. Mathematica Scandinavica, Berkeley, CA, United States, v. 16, p. 97–115, 1965. DOI: 10.7146/math.scand.a-10751. Disponível em: https://journals.msp.org/mscand/article/view/2572. Acesso em: 25 jul. 2026.