1. Agol, I., Groves, D., Manning, J.: The virtual Haken conjecture. arXiv:1204.2810v1 (2012)
2. Atiyah, M.F.: Elliptic Operators, Discrete Groups and von Neumann Algebras, Colloque “Analyse et Topologie” en l’Honneur de Henri Cartan (Orsay, 1974) Soc. Math. France, Paris. pp. 43–72 (1976). (Astérisque, No. 32–33)
3. Austin, T.: Rational group ring elements with kernels having irrational dimension. arXiv.org:0909. 2360v2 (2009)
4. Farkas, D.: Miscellany on Bieberbach group algebras. Pac. J. Math. 59(2), 427–435 ((1975))
5. Grabowski, Ł.: On the Atiyah problem for the lamplighter groups. arXiv.org:1009.0229 (2010)