@article{SM_1999_190_9_a5,
     author = {E. I. Yakovlev},
     title = {Almost principal bundles},
     journal = {Sbornik. Mathematics},
     pages = {1377--1400},
     year = {1999},
     volume = {190},
     number = {9},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1999_190_9_a5/}
}