200912.4908v3 Inequities in the Shanks-Renyi Prime Number Race - An asymptotic formula for the densities

Chebyshev was the first to observe a bias in the distribution of primes in residue classes. The general phenomenon is that if a is a nonsquare\mod q and b is a square\mod q, then there tend to be more primes congruent to amodq than bmodq in initial intervals of the positive integers; more succinctly, there is a tendency for π(x;q,a) to exceed π(x;q,b). Rubinste..