@article{JRAM_1972__252_151180,
     author = {Azmi Hanna},
     title = {On the homology theory of categories. {II.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {112--127},
     publisher = {mathdoc},
     volume = {252},
     year = {1972},
     zbl = {0288.18010},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1972__252_151180/}
}