@article{DAN_1990_310_1_a6,
     author = {K. B. Sabitov},
     title = {Extremal properties of the modulus of solutions of a class of},
     journal = {Doklady Akademii Nauk},
     pages = {33--36},
     publisher = {mathdoc},
     volume = {310},
     number = {1},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1990_310_1_a6/}
}