References
- Conformal Invariants. Topics in Geometric Function Theory Ahlfors, L.V.
- Complex Analysis Ahlfors, L.V.
- Acta. Math. v.83 Ahlfors, L.V.;Beurling, A.
- The Theory of Cluster Set Collingwood, E.F.;Lohwater, A.J.
- Encyclopedic Dictionary of Mathematics, by the Mathematical Society of Japan Kiyosi Ito
- Elements of the Theory of Functions Knop, K.
- Dirichlet Problem, Extremal Length, and Prime Ends Ohtsuka, M.
- Bull. Amer. Math. Soc. v.80 The method of extremal length Rodin, B.
- Amer. J. Math. v.74 Properties of conformal invariants Wolontis, V.
- Conformal Mapping Nehari, Z.