@article{MZM_2007_82_5_a1,
     author = {V. M. Bruk},
     title = {On {Invertible} {Contractions} of {Quotients} {Generated} by a {Differential} {Expression} and by a {Nonnegative} {Operator} {Function}},
     journal = {Matemati\v{c}eskie zametki},
     pages = {652--664},
     publisher = {mathdoc},
     volume = {82},
     number = {5},
     year = {2007},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_2007_82_5_a1/}
}