@article{DAN_1974_215_1_a14,
     author = {E. V. Shikin},
     title = {On global isometric imbedding in $\mathbf{R}^3$ of some metrics of nonpositive curvature},
     journal = {Doklady Akademii Nauk},
     pages = {61--63},
     publisher = {mathdoc},
     volume = {215},
     number = {1},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1974_215_1_a14/}
}