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://www.mscand.dk/article/view/12108. Acesso em: 5 may. 2024.