1. Afshordi, N., Aslanbeigi, S., Sorkin, R.D.: A distinguished vacuum state for a quantum field in a curved spacetime: formalism, features, and cosmology. JHEP 08, 137 (2012)
2. Araki, H.: Mathematical Theory of Quantum Fields. Oxford University Press, Oxford (1999)
3. Ashtekar, A., Magnon, A.: Quantum fields in curved space-times. Proc. Roy. Soc. Lond. A 346, 375–394 (1975)
4. Bär, C., Ginoux, N., Pfäffle, F.: Wave equations on Lorentzian manifolds and quantization. European Mathematical Society (EMS), Zürich (2007)
5. Barata, J., Jäkel, C., Mund, J.: The $${\fancyscript {P}}(\varphi )_2$$ model on de Sitter space (2013). arXiv:1311.2905 [math-ph]