@article{ZVMMF_2004_44_6_a5,
     author = {V. S. Gavrilov and M. I. Sumin},
     title = {Parametric optimization of nonlinear {Goursat{\textendash}Darboux} systems with phase constraints},
     journal = {\v{Z}urnal vy\v{c}islitelʹnoj matematiki i matemati\v{c}eskoj fiziki},
     pages = {1002--1022},
     year = {2004},
     volume = {44},
     number = {6},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/ZVMMF_2004_44_6_a5/}
}