@article{DAN_1971_199_5_a8,
     author = {S. F. Prokoptsev},
     title = {Some properties of linear combinations of functions close to exponential functions},
     journal = {Doklady Akademii Nauk},
     pages = {1018--1021},
     publisher = {mathdoc},
     volume = {199},
     number = {5},
     year = {1971},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1971_199_5_a8/}
}