%0 Journal Article %A S. Gurak %T Exponential sums of the form $\sum \chi (x)^{ax} \zeta _{m}^{bx}$ %J Acta Arithmetica %D 2007 %P 239-259 %V 126 %N 3 %I mathdoc %U http://geodesic.mathdoc.fr/articles/10.4064/aa126-3-3/ %R 10.4064/aa126-3-3 %G en %F 10_4064_aa126_3_3