@article{CMH_1972__47_139531,
     author = {F. Bachmann and L. Gr\"unenfelder},
     title = {Homological {Methods} and the {Third} {Dimension} {Subgroup}},
     journal = {Commentarii mathematici Helvetici},
     pages = {526--531},
     publisher = {mathdoc},
     volume = {47},
     year = {1972},
     zbl = {0254.20036},
     url = {http://geodesic.mathdoc.fr/item/CMH_1972__47_139531/}
}