@article{GDZPPN002304597,
title = {Roots of Unity and Covering Sets.},
journal = {Mathematische Annalen},
volume = {193},
year = {1971},
pages = {279-282},
zbl = {0203.35205},
url = {http://dml.mathdoc.fr/item/GDZPPN002304597}
}
NEWMAN, M. Roots of Unity and Covering Sets.. Mathematische Annalen, Tome 193 (1971) pp. 279-282. http://gdmltest.u-ga.fr/item/GDZPPN002304597/