@article{GDZPPN002416670,
title = {Branched Immersions of Surfaces and Reduction of Topological Type, I.},
journal = {Mathematische Zeitschrift},
volume = {142},
year = {1975},
pages = {267-288},
zbl = {0299.57014},
url = {http://dml.mathdoc.fr/item/GDZPPN002416670}
}
Gulliver, Robert. Branched Immersions of Surfaces and Reduction of Topological Type, I.. Mathematische Zeitschrift, Tome 142 (1975) pp. 267-288. http://gdmltest.u-ga.fr/item/GDZPPN002416670/