@article{DE_2001_37_6_a15,
     author = {G. A. Kurina},
     title = {Invertibility of {Nonnegatively} {Hamiltonian} {Operators} in a {Hilbert} {Space}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {839--841},
     publisher = {mathdoc},
     volume = {37},
     number = {6},
     year = {2001},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_2001_37_6_a15/}
}