Bombieri, Friedlander, Iwaniec

Primes in Arithmetic Progressions to Large Moduli. https://projecteuclid.org/journals/acta-mathematica/volume-156/issue-none/Primes-in-arithmetic-progressions-to-large-moduli/10.1007/BF02399204.full

Primes in Arithmetic Progressions to Large Moduli. II. https://eudml.org/doc/164255
Primes in Arithmetic Progressions to Large Moduli. III https://www.ams.org/journals/jams/1989-02-02/S0894-0347-1989-0976723-6/

Dipsersion, sums of Kloosterman sums