@article{DAN_1971_196_2_a1,
     author = {P. A. Biluta and S. L. Krushkal'},
     title = {On extremal quasi-conformal mappings},
     journal = {Doklady Akademii Nauk},
     pages = {259--262},
     publisher = {mathdoc},
     volume = {196},
     number = {2},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_196_2_a1/}
}