@article{MZM_1986_39_1_a1,
     author = {V. G. Sheretov},
     title = {Tests for extremality in a problem for quasiconformal mappings},
     journal = {Matemati\v{c}eskie zametki},
     pages = {14--23},
     publisher = {mathdoc},
     volume = {39},
     number = {1},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1986_39_1_a1/}
}