@article{CMH_1973__48_139547,
     author = {John N. Mather},
     title = {Integrability in {Codimension} 1},
     journal = {Commentarii mathematici Helvetici},
     pages = {195--233},
     publisher = {mathdoc},
     volume = {48},
     year = {1973},
     zbl = {0284.57016},
     url = {http://geodesic.mathdoc.fr/item/CMH_1973__48_139547/}
}