@article{JRAM_1993__445_153580,
     author = {U. Zannier},
     title = {Ritt's {Second} {Theorem} in arbitrary characteristic.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {175--204},
     publisher = {mathdoc},
     volume = {445},
     year = {1993},
     zbl = {0786.12001},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1993__445_153580/}
}