@article{MAN_1977__230_163027,
     author = {Robert Gulliver},
     title = {Branched {Immersions} of {Surfaces} and {Reduction} of {Topological} {Type.} {II.}},
     journal = {Mathematische Annalen},
     pages = {25--48},
     year = {1977},
     volume = {230},
     zbl = {0338.57014},
     url = {http://geodesic.mathdoc.fr/item/MAN_1977__230_163027/}
}