@article{JRAM_1969__238_183510,
     author = {J.W.S. Cassels},
     title = {On a conjecture of {R.M.} {Robinson} about sums of roots of unity.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {112--131},
     publisher = {mathdoc},
     volume = {238},
     year = {1969},
     zbl = {0179.35203},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1969__238_183510/}
}