@article{GDZPPN002421690, title = {A Hopf Inequality for Branch Sets.}, journal = {Mathematische Zeitschrift}, volume = {162}, year = {1978}, pages = {81-92}, zbl = {0373.55002}, url = {http://dml.mathdoc.fr/item/GDZPPN002421690} }
DeGeorge, David L.; Reddy, William L. A Hopf Inequality for Branch Sets.. Mathematische Zeitschrift, Tome 162 (1978) pp. 81-92. http://gdmltest.u-ga.fr/item/GDZPPN002421690/