@article{SM_1972_17_3_a4,
     author = {M. L. Gromov},
     title = {Smoothing and inversion of differential operators},
     journal = {Sbornik. Mathematics},
     pages = {381--435},
     year = {1972},
     volume = {17},
     number = {3},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1972_17_3_a4/}
}