@article{DE_1975_11_1_a8,
     author = {V. M. Isakov},
     title = {Inverse theorems on the smoothness of potentials},
     journal = {Differencialʹnye uravneni\^a},
     pages = {66--74},
     publisher = {mathdoc},
     volume = {11},
     number = {1},
     year = {1975},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1975_11_1_a8/}
}