@article{CMH_1969__44_139404,
     author = {John R. Harper},
     title = {Stable {Secondary} {Cohomology} {Operations.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {341--353},
     year = {1969},
     volume = {44},
     zbl = {0199.33202},
     url = {http://geodesic.mathdoc.fr/item/CMH_1969__44_139404/}
}