@article{SM_1971_15_2_a1,
     author = {G. A. Kats},
     title = {On some characteristic classes in the category of smooth $G$-fiberings},
     journal = {Sbornik. Mathematics},
     pages = {176--182},
     publisher = {mathdoc},
     volume = {15},
     number = {2},
     year = {1971},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1971_15_2_a1/}
}