@article{TIMB_2007_15_1_a4,
     author = {A. V. Guminskaya and P. P. Zabreiko},
     title = {On {Hopf's} theorems for relative rotation},
     journal = {Trudy Instituta matematiki},
     pages = {33--46},
     publisher = {mathdoc},
     volume = {15},
     number = {1},
     year = {2007},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TIMB_2007_15_1_a4/}
}