@article{IVM_2021_4_a2,
     author = {T. A. Gonchar and E. I. Yakovlev},
     title = {Coverings in the category of principal bundles},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {25--47},
     publisher = {mathdoc},
     number = {4},
     year = {2021},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_2021_4_a2/}
}