1. Kostelecky, V.A.: Prepared for 3rd Meeting on CPT and Lorentz Symmetry (CPT 04), Bloomington, Indiana, 8–11 August 2007 and references therein
2. Jacobson, T., Liberati, S., Mattingly, D.: Ann. Phys. 321, 150 (2006). arXiv: astro-ph/0505267 and references therein
3. Amelino-Camelia, G.: arXiv: 0806.0339 [gr-qc] and references therein
4. Lüders, G.: Ann. Phys. (NY) 2, 1 (1957)
5. Jost, R.: Helv. Phys. Acta 30, 409 (1957)