@article{GDZPPN00210301X, title = {Bounds on the number of non-rational subfields of a function field.}, journal = {Inventiones mathematicae}, volume = {83}, year = {1986}, pages = {185-198}, zbl = {0615.12017}, url = {http://dml.mathdoc.fr/item/GDZPPN00210301X} }
Kani, E. Bounds on the number of non-rational subfields of a function field.. Inventiones mathematicae, Tome 83 (1986) pp. 185-198. http://gdmltest.u-ga.fr/item/GDZPPN00210301X/