@incollection{SB_1971-1972__14__239_0,
     author = {Haefliger, Andr\'e},
     title = {Sur les classes caract\'eristiques des feuilletages},
     booktitle = {S\'eminaire Bourbaki : vol. 1971/72, expos\'es 400-417},
     series = {S\'eminaire Bourbaki},
     note = {talk:412},
     pages = {239--260},
     year = {1973},
     publisher = {Springer-Verlag},
     address = {Berlin/Heidelberg},
     number = {14},
     mrnumber = {420655},
     zbl = {0257.57011},
     language = {fr},
     url = {https://www.numdam.org/item/SB_1971-1972__14__239_0/}
}