@article{DE_1973_9_2_a3,
     author = {I. D. Evzerov and P. E. Sobolevskii},
     title = {Fractional powers of ordinary differential operators},
     journal = {Differencialʹnye uravneni\^a},
     pages = {228--240},
     publisher = {mathdoc},
     volume = {9},
     number = {2},
     year = {1973},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1973_9_2_a3/}
}