@article{JRAM_1978__298_151970,
     author = {S. Chowla and J. Cowles and M. Cowles},
     title = {Congruence properties of the number of solutions of some equations.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {101--103},
     publisher = {mathdoc},
     volume = {298},
     year = {1978},
     zbl = {0366.10019},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1978__298_151970/}
}