@article{SM_1975_25_1_a4,
     author = {A. V. Shokurov},
     title = {On the homotopy and homology realization of exact sequences of groups},
     journal = {Sbornik. Mathematics},
     pages = {77--86},
     publisher = {mathdoc},
     volume = {25},
     number = {1},
     year = {1975},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1975_25_1_a4/}
}