@article{GDZPPN002062984, title = {Quadruple points of 3-manifolds in S4.}, journal = {Commentarii mathematici Helvetici}, volume = {53}, year = {1978}, pages = {385-394}, zbl = {0404.57011}, url = {http://dml.mathdoc.fr/item/GDZPPN002062984} }
Freedman, Michael H. Quadruple points of 3-manifolds in S4.. Commentarii mathematici Helvetici, Tome 53 (1978) pp. 385-394. http://gdmltest.u-ga.fr/item/GDZPPN002062984/