@article{IM_1977__43_142508,
     author = {H.L. Montgomery and R.C. Vaughan},
     title = {Exponential {Sums} with {Multiplicative} {Coefficients.}},
     journal = {Inventiones mathematicae},
     pages = {69--82},
     year = {1977},
     volume = {43},
     zbl = {0362.10036},
     url = {http://geodesic.mathdoc.fr/item/IM_1977__43_142508/}
}