@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/}
}