@article{10_4153_CMB_1964_058_9,
     author = {Scherk, P.},
     title = {On the {Exactness} of the {Homotopy} {Sequence}},
     journal = {Canadian mathematical bulletin},
     pages = {617--618},
     year = {1964},
     volume = {7},
     number = {4},
     doi = {10.4153/CMB-1964-058-9},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1964-058-9/}
}