@article{DE_1986_22_11_a12,
     author = {K. B. Mansimov},
     title = {Optimality of quasisingular controls in {Goursat--Darboux} systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1952--1960},
     publisher = {mathdoc},
     volume = {22},
     number = {11},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1986_22_11_a12/}
}