Quantum-invariant theory and the evolution of a Dirac field in Friedmann–Robertson–Walker flat space-times Xiao-Chun Gao, Jian Fu and Jian-Qi ShenEur. Phys. J. C, 13 3 (2000) 527-541DOI: https://doi.org/epjc/v13/p527(epjc0257)