@article{10_4153_CMB_1967_002_8,
     author = {Seip, Ulrich},
     title = {Categorical {Fibrations}},
     journal = {Canadian mathematical bulletin},
     pages = {5--17},
     year = {1967},
     volume = {10},
     number = {1},
     doi = {10.4153/CMB-1967-002-8},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1967-002-8/}
}