@article{DAN_1977_236_3_a4,
     author = {Yu. A. Kaz'min},
     title = {The closures of the linear spans of two systems of functions},
     journal = {Doklady Akademii Nauk},
     pages = {535--537},
     publisher = {mathdoc},
     volume = {236},
     number = {3},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1977_236_3_a4/}
}