Covering Theorems for Univalent Functions Mapping onto Domains Bounded by Quasiconformal Circles

Abstract

Let Γ be a Jordan curve in the extended complex plane C. Γ is called a quasiconformal circle if it is the image of a circle by a homeomorphism ƒ which is quasiconformal in a neighborhood of that circle. If q(zi, z2) is the chordal distance from z1 to z2, the chordal cross ratio of a quadruple z1, z2, z3, z4 in C is