@article{DE_1969_5_7_a8,
     author = {R. S. Levitin},
     title = {Frommer's first distinguishing problem for perturbations from {Osgood} and {Tamarkin} classes},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1236--1246},
     publisher = {mathdoc},
     volume = {5},
     number = {7},
     year = {1969},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1969_5_7_a8/}
}