@article{DAN_1958_123_6_a7,
     author = {P. E. Sobolevskii},
     title = {First order differential equations in {Hilbert} space with a variable positively defined self-adjoined operator whose fractional power has a constant definition domain},
     journal = {Doklady Akademii Nauk},
     pages = {984--987},
     publisher = {mathdoc},
     volume = {123},
     number = {6},
     year = {1958},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1958_123_6_a7/}
}