@article{SM_1991_70_1_a3,
     author = {A. I. Tret'yak},
     title = {On necessary conditions for odd optimability of high speed prbblem for the linear on control systems},
     journal = {Sbornik. Mathematics},
     pages = {47--63},
     publisher = {mathdoc},
     volume = {70},
     number = {1},
     year = {1991},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1991_70_1_a3/}
}