@article{DAN_1990_315_1_a1,
     author = {A. L. Bukhgeim and S. G. Kazantsev},
     title = {Elliptic systems of {Beltrami} type and tomography problems},
     journal = {Doklady Akademii Nauk},
     pages = {15--19},
     publisher = {mathdoc},
     volume = {315},
     number = {1},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1990_315_1_a1/}
}