1. B.S. DeWitt, Dynamical Theory of Groups and Fields (Gordon and Breach, New York, 1965); The Global Approach to Quantum Field Theory vol. 1 and 2 (Clarendon Press, Oxford, 2003)
2. n.d. Birell, P.C.W. Davies, Quantum Fields in Curved Space (Cambridge University Press, Cambridge, 1982)
3. I.L. Buchbinder, S.D. Odintsov, I.L. Shapiro, Effective Action in Quantum Gravity (IOP Publishing, Bristol, 1992)
4. V. Mukhanov, S. Winitzki, Introduction to quantum effects in gravity (Cambridge University Press, Cambridge, 2007)
5. L. Parker, D.J. Toms, Quantum Field Theory in Curved Spacetime: Quantized Fields and Gravity (Cambridge University Press, Cambridge, 2014)