Bilinear Forms with Exponential Sums with Binomials
  We obtain several estimates for bilinear form with exponential sums with binomials $mx^k + nx^\ell$. In particular we show the existence of nontrivial cancellations between such sums when the coefficients $m$ and $n$ vary over rather sparse sets of general nature 
Kui Liu, Igor E. Shparlinski and Tianping Zhang
math.NT