Schuller, Frederic P. Quantum Gravity & Unified Theories, AEI-Golm, MPI for Gravitational Physics, Max Planck Society;
AoP2010.04.008.pdf (Any fulltext), 361KB
Schuller, F. P., Witte, C., & Wohlfarth, M. N. (2010). Causal structure and algebraic classification of non-dissipative linear optical media. Annals of Physics, 325(9), 1853-1883. doi:10.1016/j.aop.2010.04.008.