@article{10_1090_S0894_0347_07_00561_9,
     author = {Linnell, Peter and Schick, Thomas},
     title = {Finite group extensions and the {Atiyah} conjecture},
     journal = {Journal of the American Mathematical Society},
     pages = {1003--1051},
     publisher = {mathdoc},
     volume = {20},
     number = {4},
     year = {2007},
     doi = {10.1090/S0894-0347-07-00561-9},
     url = {http://geodesic.mathdoc.fr/articles/10.1090/S0894-0347-07-00561-9/}
}