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@article{FAA_1991_25_3_a0, author = {N. A. Bobylev and Yu. M. Burman}, title = {Morse lemma for functionals of variational calculus}, journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a}, pages = {1--11}, publisher = {mathdoc}, volume = {25}, number = {3}, year = {1991}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/FAA_1991_25_3_a0/} }
N. A. Bobylev; Yu. M. Burman. Morse lemma for functionals of variational calculus. Funkcionalʹnyj analiz i ego priloženiâ, Tome 25 (1991) no. 3, pp. 1-11. http://geodesic.mathdoc.fr/item/FAA_1991_25_3_a0/