@article{MZM_1990_48_2_a3,
     author = {R. I. Grigorchuk and P. F. Kurchanov},
     title = {Classification of epimorphisms of fundamental groups of surfaces onto free groups},
     journal = {Matemati\v{c}eskie zametki},
     pages = {26--35},
     publisher = {mathdoc},
     volume = {48},
     number = {2},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1990_48_2_a3/}
}