Contents xi 8.3.2 A Mellin-Barnes Integral Representation 8.3.3 Asymptotics ofP (x, y) for |x| → ∞ 8.3.4 Asymptotics ofP (x, y) for |y| → ∞ 8.3.5 Asymptotics of P (X, Y) for Real X, Y 8.3.6 Generalisations of P (X, Y) Appendix References Index † We note here that li(x) is also used to denote the same integral, but taken over the interval (0, x), with x > 1. With this larger interval, the integral is a Cauchy principal value integral. The notation in this example appears to be in use by some number theorists, and is also sometimes written Li(x).