@article{CTGDC_1983__24_2_193_0,
     author = {M\"uller, Thomas},
     title = {Note on homotopy pullbacks in abelian categories},
     journal = {Cahiers de Topologie et G\'eom\'etrie Diff\'erentielle Cat\'egoriques},
     pages = {193--202},
     publisher = {Dunod \'editeur, publi\'e avec le concours du CNRS},
     volume = {24},
     number = {2},
     year = {1983},
     mrnumber = {710040},
     zbl = {0515.18007},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/CTGDC_1983__24_2_193_0/}
}