@article{TRSPY_1987_180_a73,
     author = {B. S. Kashin},
     title = {On trigonometric polynomials with coefficients $+1$, $-1$,~$0$},
     journal = {Informatics and Automation},
     pages = {131--132},
     publisher = {mathdoc},
     volume = {180},
     year = {1987},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TRSPY_1987_180_a73/}
}