@article{DE_1974_10_4_a2,
     author = {L. T. Ashchepkov and D. S. \`Eppel'},
     title = {An analogue of {Kelley's} condition in optimal systems with lag},
     journal = {Differencialʹnye uravneni\^a},
     pages = {591--597},
     publisher = {mathdoc},
     volume = {10},
     number = {4},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1974_10_4_a2/}
}