@article{MS2_1994__74_1_167290,
     author = {Georges Hoff},
     title = {Cohomologies et extensions de cat\'egories.},
     journal = {Mathematica Scandinavica},
     pages = {191--207},
     year = {1994},
     volume = {74},
     number = {1},
     zbl = {0823.18007},
     url = {http://geodesic.mathdoc.fr/item/MS2_1994__74_1_167290/}
}