@article{GDZPPN002186411,
title = {The spherical derivative of meromorphic functions.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {253},
year = {1972},
pages = {51-67},
zbl = {0226.30033},
url = {http://dml.mathdoc.fr/item/GDZPPN002186411}
}
Dragosh, Stephen. The spherical derivative of meromorphic functions.. Journal für die reine und angewandte Mathematik, Tome 253 (1972) pp. 51-67. http://gdmltest.u-ga.fr/item/GDZPPN002186411/