@article{SM_1967_1_2_a6,
     author = {V. A. Sadovnichii},
     title = {The trace of ordinary differential operators of high order},
     journal = {Sbornik. Mathematics},
     pages = {263--288},
     year = {1967},
     volume = {1},
     number = {2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1967_1_2_a6/}
}