@article{MZM_2004_75_1_a1,
     author = {S. A. Bogatyi and D. L. Gon\c{c}alves and E. A. Kudryavtseva and H. Zieschang},
     title = {Minimal {Number} of {Preimages} {Under} {Maps} of {Surfaces}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {13--19},
     publisher = {mathdoc},
     volume = {75},
     number = {1},
     year = {2004},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2004_75_1_a1/}
}