@article{IM2_1971_5_6_a1,
     author = {A. F. Lavrik},
     title = {A~method for estimating double sums with real quadratic character, and applications},
     journal = {Izvestiya. Mathematics},
     pages = {1195--1214},
     year = {1971},
     volume = {5},
     number = {6},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/IM2_1971_5_6_a1/}
}