@incollection{SB_1988-1989__31__155_0,
     author = {Ghys, \'Etienne},
     title = {L'invariant de {Godbillon-Vey}},
     booktitle = {S\'eminaire Bourbaki : volume 1988/89, expos\'es 700-714},
     series = {Ast\'erisque},
     note = {talk:706},
     pages = {155--181},
     publisher = {Soci\'et\'e math\'ematique de France},
     number = {177-178},
     year = {1989},
     mrnumber = {1040572},
     zbl = {0707.57015},
     language = {fr},
     url = {http://archive.numdam.org/item/SB_1988-1989__31__155_0/}
}