@article{IM_1990__102_2_143826,
     author = {Lluis Puig and Burkhard K\"ulshammer},
     title = {Extensions of nilpotent blocks.},
     journal = {Inventiones mathematicae},
     pages = {17--72},
     publisher = {mathdoc},
     volume = {102},
     number = {2},
     year = {1990},
     zbl = {0739.20003},
     url = {http://geodesic.mathdoc.fr/item/IM_1990__102_2_143826/}
}