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@article{MZM_1990_48_1_a9, author = {\"U. G. Lumiste}, title = {Absence of complete {Lobachevskii} planes in two classes of surfaces in~$E_4$ with~$K=-1$}, journal = {Matemati\v{c}eskie zametki}, pages = {68--74}, publisher = {mathdoc}, volume = {48}, number = {1}, year = {1990}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/MZM_1990_48_1_a9/} }
Ü. G. Lumiste. Absence of complete Lobachevskii planes in two classes of surfaces in~$E_4$ with~$K=-1$. Matematičeskie zametki, Tome 48 (1990) no. 1, pp. 68-74. http://geodesic.mathdoc.fr/item/MZM_1990_48_1_a9/