@article{GDZPPN002414244, title = {Universal Covering Maps for Variable Regions.}, journal = {Mathematische Zeitschrift}, volume = {136}, year = {1974}, pages = {7-20}, zbl = {0316.30009}, url = {http://dml.mathdoc.fr/item/GDZPPN002414244} }
Hejhal, Dennis A. Universal Covering Maps for Variable Regions.. Mathematische Zeitschrift, Tome 136 (1974) pp. 7-20. http://gdmltest.u-ga.fr/item/GDZPPN002414244/