@article{MZM_1981_30_5_a6,
     author = {V. A. Khatskevich},
     title = {Invariant subspaces of focusing plus-operators},
     journal = {Matemati\v{c}eskie zametki},
     pages = {695--702},
     publisher = {mathdoc},
     volume = {30},
     number = {5},
     year = {1981},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1981_30_5_a6/}
}