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@article{MZM_1979_25_5_a14, author = {E. V. Shikin}, title = {Isometric imbedding in $E^3$ of noncompact domains of nonpositive curvature}, journal = {Matemati\v{c}eskie zametki}, pages = {785--797}, publisher = {mathdoc}, volume = {25}, number = {5}, year = {1979}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1979_25_5_a14/} }
E. V. Shikin. Isometric imbedding in $E^3$ of noncompact domains of nonpositive curvature. Matematičeskie zametki, Tome 25 (1979) no. 5, pp. 785-797. http://geodesic.mathdoc.fr/item/MZM_1979_25_5_a14/