@article{FPM_2007_13_6_a4,
     author = {I. V. Artamkin},
     title = {Combinatorics of trivalent ribbon graphs with two faces},
     journal = {Fundamentalʹna\^a i prikladna\^a matematika},
     pages = {113--120},
     publisher = {mathdoc},
     volume = {13},
     number = {6},
     year = {2007},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/FPM_2007_13_6_a4/}
}