@article{GDZPPN002211211,
title = {Ritt's Second Theorem in arbitrary characteristic.},
journal = {Journal f\"ur die reine und angewandte Mathematik},
volume = {435},
year = {1993},
pages = {175-204},
zbl = {0786.12001},
url = {http://dml.mathdoc.fr/item/GDZPPN002211211}
}
Zannier, U. Ritt's Second Theorem in arbitrary characteristic.. Journal für die reine und angewandte Mathematik, Tome 435 (1993) pp. 175-204. http://gdmltest.u-ga.fr/item/GDZPPN002211211/