@article{10_4007_annals_2006_163_809,
     author = {Sorin Popa},
     title = {On a class of type $II_1$ factors with {Betti} numbers invariants},
     journal = {Annals of mathematics},
     pages = {809--899},
     publisher = {mathdoc},
     volume = {163},
     number = {3},
     year = {2006},
     doi = {10.4007/annals.2006.163.809},
     mrnumber = {2215135},
     zbl = {1120.46045},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4007/annals.2006.163.809/}
}