1. Lectures on Quantum Mechanics;Dirac,1964
2. Quantization of Gauge Systems;Henneaux,1992
3. Time and interpretations of quantum gravity;Kuchař;Int. J. Mod. Phys. Proc. Suppl. D,2011
4. Canonical quantum gravity and the problem of time;Isham,1993
5. Problem of time in quantum gravity;Anderson;Ann. Phys.,2012