@article{10_4064_aa97_3_2,
     author = {Hong Bing Yu},
     title = {Estimates of character sums with exponential function},
     journal = {Acta Arithmetica},
     pages = {211--218},
     year = {2001},
     volume = {97},
     number = {3},
     doi = {10.4064/aa97-3-2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/aa97-3-2/}
}