@article{DE_1966_2_10_a5,
     author = {N. P. Erugin},
     title = {On the theory of canonical systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1317--1332},
     publisher = {mathdoc},
     volume = {2},
     number = {10},
     year = {1966},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1966_2_10_a5/}
}