@article{DAN_1960_132_5_a12,
     author = {A. F. Leont'ev},
     title = {On convexity of the region in which the solution of a differential equation of infinite order is regular},
     journal = {Doklady Akademii Nauk},
     pages = {1019--1022},
     publisher = {mathdoc},
     volume = {132},
     number = {5},
     year = {1960},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1960_132_5_a12/}
}