@article{IM2_1973_7_2_a5,
     author = {M. L. Gromov},
     title = {Convex integration of differential {relations.~I}},
     journal = {Izvestiya. Mathematics },
     pages = {329--343},
     publisher = {mathdoc},
     volume = {7},
     number = {2},
     year = {1973},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1973_7_2_a5/}
}