@article{DAN_1972_204_2_a1,
     author = {E. G. Bam-Zelikovich},
     title = {Some necessary conditions for local solvability of first-order differential equations with infinitely differentiable coefficients},
     journal = {Doklady Akademii Nauk},
     pages = {267--270},
     publisher = {mathdoc},
     volume = {204},
     number = {2},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1972_204_2_a1/}
}