@article{MS_1964__106_4_a2,
     author = {{\CYRV}.{\CYREREV}. {\CYRL}{\cyrya}{\cyrn}{\cyrc}{\cyre}},
     title = {A differential operator with spectral singularities. {I}},
     journal = {Matemati\v{c}eskij sbornik},
     pages = {521--561},
     publisher = {mathdoc},
     volume = {106},
     number = {4},
     year = {1964},
     zbl = {0189.38102},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/MS_1964__106_4_a2/}
}