@article{DE_1974_10_6_a7,
     author = {V. A. Srochko},
     title = {An investigation of the second variation on singular controls},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1050--1066},
     publisher = {mathdoc},
     volume = {10},
     number = {6},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1974_10_6_a7/}
}