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@article{DAN_1990_313_2_a1, author = {V. F. Lazutkin}, title = {The width of the instability zone around separatrices of a}, journal = {Doklady Akademii Nauk}, pages = {268--272}, publisher = {mathdoc}, volume = {313}, number = {2}, year = {1990}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/DAN_1990_313_2_a1/} }
V. F. Lazutkin. The width of the instability zone around separatrices of a. Doklady Akademii Nauk, Tome 313 (1990) no. 2, pp. 268-272. http://geodesic.mathdoc.fr/item/DAN_1990_313_2_a1/