@article{GDZPPN002059576, title = {Stable Secondary Cohomology Operations.}, journal = {Commentarii mathematici Helvetici}, volume = {44}, year = {1969}, pages = {341-353}, zbl = {0199.33202}, url = {http://dml.mathdoc.fr/item/GDZPPN002059576} }
Harper, John R. Stable Secondary Cohomology Operations.. Commentarii mathematici Helvetici, Tome 44 (1969) pp. 341-353. http://gdmltest.u-ga.fr/item/GDZPPN002059576/