(91) has a well-defined limit for b → 0, provided the limits lim x→0 H(p, x) exist. H(-p, x) and H(0, x) are problematic, since they contain terms of the form x -i with i ≥ 1 2 , which diverge in the limit x → 0. For negative -p we use Eqn. (89) to rewrite Eqn. (39') in as