@article{MAT_1970_14_2_a2,
     author = {D. C. Spencer},
     title = {Overdetermined systems of linear partial differential equations},
     journal = {Matematika},
     pages = {66--90},
     year = {1970},
     volume = {14},
     number = {2},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MAT_1970_14_2_a2/}
}