@article{DE_1966_2_12_a6,
     author = {V. A. Sadovnichy},
     title = {On the trace of the difference of two ordinary differential operators of higher orders},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1611--1624},
     publisher = {mathdoc},
     volume = {2},
     number = {12},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1966_2_12_a6/}
}