@article{MAN_1971__191_162138,
     author = {M. NEWMAN},
     title = {Roots of {Unity} and {Covering} {Sets.}},
     journal = {Mathematische Annalen},
     pages = {279--282},
     publisher = {mathdoc},
     volume = {191},
     year = {1971},
     zbl = {0203.35205},
     url = {http://geodesic.mathdoc.fr/item/MAN_1971__191_162138/}
}