HOLTZMAN, D. N. Pyramids of higher order cohomology operations in the $p$-torsion-free category. MATHEMATICA SCANDINAVICA, [S. l.], v. 57, p. 127–154, 1985. DOI: 10.7146/math.scand.a-12108. Disponível em: https://tidsskrift.dk/math/article/view/12108. Acesso em: 14 aug. 2026.