@article{10_4064_fm_50_3_265_279,
     author = {I. Berstein and Tudor Ganea},
     title = {The category of a map and of a cohomology class},
     journal = {Fundamenta Mathematicae},
     pages = {265--279},
     publisher = {mathdoc},
     volume = {50},
     number = {3},
     year = {1961},
     doi = {10.4064/fm-50-3-265-279},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/fm-50-3-265-279/}
}