@article{DAN_1986_286_4_a7,
     author = {K. B. Mansimov},
     title = {On the optimality of controls singular in the classical sense in {Goursat--Darboux} systems},
     journal = {Doklady Akademii Nauk},
     pages = {808--812},
     publisher = {mathdoc},
     volume = {286},
     number = {4},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1986_286_4_a7/}
}