@article{DAN_1991_316_1_a7,
     author = {M. Yu. Zvyagin},
     title = {Second order equations reducible to $z_{xy}=0$ by a {B\"acklund} transformation},
     journal = {Doklady Akademii Nauk},
     pages = {36--40},
     publisher = {mathdoc},
     volume = {316},
     number = {1},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_316_1_a7/}
}