@article{CMH_1961__35_139209,
     author = {P.J. Hilton},
     title = {On excision and principal fibrations.},
     journal = {Commentarii mathematici Helvetici},
     pages = {77--84},
     publisher = {mathdoc},
     volume = {35},
     year = {1961},
     zbl = {0107.16804},
     url = {http://geodesic.mathdoc.fr/item/CMH_1961__35_139209/}
}