@article{MS2_1985__57_166946,
     author = {D.N. Holtzman},
     title = {Product structures in pyramids of higher order cohomology operations.},
     journal = {Mathematica Scandinavica},
     pages = {155--170},
     year = {1985},
     volume = {57},
     zbl = {0562.55019},
     url = {http://geodesic.mathdoc.fr/item/MS2_1985__57_166946/}
}