@article{CRMATH_2004__339_7_463_0,
     author = {Bourgain, Jean and Chang, Mei-Chu},
     title = {Sum-product theorem and exponential sum estimates in residue classes with modulus involving few prime factors},
     journal = {Comptes Rendus. Math\'ematique},
     pages = {463--466},
     publisher = {Elsevier},
     volume = {339},
     number = {7},
     year = {2004},
     doi = {10.1016/j.crma.2004.08.007},
     language = {en},
     url = {http://www.numdam.org/articles/10.1016/j.crma.2004.08.007/}
}