@article{DAN_1960_131_2_a12,
     author = {G. I. Trushin},
     title = {Third order conjugate systems and the problem of their focal transformations},
     journal = {Doklady Akademii Nauk},
     pages = {265--268},
     publisher = {mathdoc},
     volume = {131},
     number = {2},
     year = {1960},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1960_131_2_a12/}
}