@article{GDZPPN002418649,
title = {Extremal Length and Univalent Functions, I. The Angular Derivative.},
journal = {Mathematische Zeitschrift},
volume = {154},
year = {1977},
pages = {1-18},
zbl = {0384.30006},
url = {http://dml.mathdoc.fr/item/GDZPPN002418649}
}
Rodin, Burton; Warschawski, Stefan E. Extremal Length and Univalent Functions, I. The Angular Derivative.. Mathematische Zeitschrift, Tome 154 (1977) pp. 1-18. http://gdmltest.u-ga.fr/item/GDZPPN002418649/