@article{IM2_1971_5_3_a1,
     author = {A. A. Karatsuba},
     title = {Sums of characters with prime numbers in an arithmetic progression},
     journal = {Izvestiya. Mathematics },
     pages = {485--501},
     publisher = {mathdoc},
     volume = {5},
     number = {3},
     year = {1971},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1971_5_3_a1/}
}