1. CMS collaboration: Phys. Lett. B 716, 30 (2012) and ATLAS collaboration: Phys. Lett. B 716, 1 (2012)
2. see e.g. Bertone, G., Hooper, D., Silk, J.: Phys. Rept. 405, 279 (2005), arXiv:hep-ph/0404175 and references therein
3. see e.g. Canetti, L. et al.: New J. Phys. 14, 095012 (2012) and references therein
4. Sakharov, A.D.: Phys. Lett. 5, 24 (1967)
5. add review here