1. N. A. Lebedev, The Area Principle in the Theory of Single-Sheeted Functions [in Russian], Nauka, Moscow (1975).
2. A. Z. Grinshpan and Z. D. Kolomoitseva, ?The area method for functions with no common values,? Vestn. Leningr. Univ., Ser. Mat., Mekh. Astron., No. 19, 31?36 (1979).
3. I. M. Milin, Single-Sheeted Functions and Orthonormed Systems [in Russian], Nauka, Moscow (1971).
4. O. Lehto, ?Schlicht functions with a quasiconformal extension,? Ann. Acad. Sci. Fenn. Suomolais Tiedeakat. Toimituks, Ser. AI,500, 10 (1971).
5. R. Kühnau, ?Verzuerrungssätze und Koeffizientenbedingungen von Grunsky'schen Typ für quasikonforme Abbildungen,? Math. Nachr.,48, 77?105 (1971).