@incollection{SB_2002-2003__45__321_0,
     author = {Connes, Alain},
     title = {Nombres de {Betti} $L^2$ et facteurs de type ${\rm II}_1$},
     booktitle = {S\'eminaire Bourbaki : volume 2002/2003, expos\'es 909-923},
     series = {Ast\'erisque},
     note = {talk:920},
     pages = {321--333},
     publisher = {Association des amis de Nicolas Bourbaki, Soci\'et\'e math\'ematique de France},
     address = {Paris},
     number = {294},
     year = {2004},
     zbl = {1133.46032},
     language = {fr},
     url = {http://www.numdam.org/item/SB_2002-2003__45__321_0/}
}