@article{CMH_1960__34_139197,
     author = {B. Eckmann and P.J. Hilton},
     title = {Homotopy {Groups} of {Maps} and {Exact} {Sequences.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {271--304},
     year = {1960},
     volume = {34},
     zbl = {0099.17904},
     url = {http://geodesic.mathdoc.fr/item/CMH_1960__34_139197/}
}