@article{SM_1967_2_1_a9,
     author = {E. M. Landis and I. G. Petrovskii},
     title = {Letter to the {Editors}},
     journal = {Sbornik. Mathematics},
     pages = {141},
     publisher = {mathdoc},
     volume = {2},
     number = {1},
     year = {1967},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/SM_1967_2_1_a9/}
}