@article{MZM_1989_45_1_a3,
     author = {A. N. Zubkov and V. T. Fomenko},
     title = {Transformations of $R$-surfaces of {Euclidean} space preserving their {Grassman} image},
     journal = {Matemati\v{c}eskie zametki},
     pages = {20--27},
     publisher = {mathdoc},
     volume = {45},
     number = {1},
     year = {1989},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1989_45_1_a3/}
}