@article{10_4064_aa118_4_6,
     author = {A. S\'ark\"ozy},
     title = {On sums and products of residues modulo $p$},
     journal = {Acta Arithmetica},
     pages = {403--409},
     publisher = {mathdoc},
     volume = {118},
     number = {4},
     year = {2005},
     doi = {10.4064/aa118-4-6},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa118-4-6/}
}