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@article{FAA_1976_10_4_a1, author = {I. M. Gel'fand and L. A. Dikii}, title = {Fractional powers of operators and {Hamiltonian} systems}, journal = {Funkcionalʹnyj analiz i ego prilo\v{z}eni\^a}, pages = {13--29}, publisher = {mathdoc}, volume = {10}, number = {4}, year = {1976}, language = {ru}, url = {http://geodesic.mathdoc.fr/item/FAA_1976_10_4_a1/} }
I. M. Gel'fand; L. A. Dikii. Fractional powers of operators and Hamiltonian systems. Funkcionalʹnyj analiz i ego priloženiâ, Tome 10 (1976) no. 4, pp. 13-29. http://geodesic.mathdoc.fr/item/FAA_1976_10_4_a1/