@article{GDZPPN002087510, title = {Non-Orientable Surfaces in Orientable 3-Manifolds.}, journal = {Inventiones mathematicae}, volume = {9}, year = {1969}, pages = {83-110}, zbl = {0175.20504}, url = {http://dml.mathdoc.fr/item/GDZPPN002087510} }
BREDON, G.E.; WOOD, J.W. Non-Orientable Surfaces in Orientable 3-Manifolds.. Inventiones mathematicae, Tome 9 (1969) pp. 83-110. http://gdmltest.u-ga.fr/item/GDZPPN002087510/