1. T. Han, Z. Liu, A. Natarajan. arXiv:1303.3040
2. A. Fowlie, K. Kowalska, L. Roszkowski, E.M. Sessolo, Y.-L.S. Tsai. arXiv:1306.1567
3. E. Ma, Phys. Rev. D 85, 091701 (2012). arXiv:1202.5828
4. W.-L. Guo, Y.-L. Wu, Y.-F. Zhou, Int. J. Mod. Phys. D 20, 1389–1397 (2011)
5. G. Belanger (Annecy, LAPTH), M. Kakizaki, A. Pukhov, JCAP 1102, 009 (2011). arXiv:1012.2577