@article{GDZPPN002067609, title = {Multiple fibres of a morphism.}, journal = {Commentarii mathematici Helvetici}, volume = {65}, year = {1990}, pages = {287-298}, zbl = {0714.14008}, url = {http://dml.mathdoc.fr/item/GDZPPN002067609} }
Serrano, Fernando. Multiple fibres of a morphism.. Commentarii mathematici Helvetici, Tome 65 (1990) pp. 287-298. http://gdmltest.u-ga.fr/item/GDZPPN002067609/