Equation Icon  u ∗= Ku , (7.4 ) B B -- --------------1 +-ζζ-------------- K = (aζ + b)(aζ-+ b) + (cζ + d)(cζ-+ d), ζ∗ = aζ-+-b; ad − bc = 1. (7.5 ) cζ + d cζ + d eiλ = ------- cζ + d