1. Bender, C.M.: Quantum Mechanics Based on Non-Hermitian Hamiltonians. In: Takei, Y. (ed) Proceedings of the International Conference “Recent Trends in Exponential Asymptotics,” Kyoto, July, 2004. RIMS Kokyuroku Symposium Series 1424, 64–77 (2005). This paper gives a background of
$$
\mathcal{P}\mathcal{T}
$$
-symmetric quantum mechanics and gives some references.
2. Bender, C.M., Brody, D.C., Jones, H.F.: Complex Extension of Quantum Mechanics, Phys. Rev. Lett. 89, 270401–4 (2002)
3. Bender, C.M., Meisinger, P.N., and Wang, Q.: Perturbative Calculation of the Hidden Symmetry Operator in
$$
\mathcal{P}\mathcal{T}
$$
-Symmetric Quantum Mechanics, J. Phys. A: Math. Gen. 36, 1973–83 (2003)
4. Bender, C.M. and Jones, H.F.: Semiclassical Calculation of the
$$
\mathcal{C}
$$
Operator in
$$
\mathcal{P}\mathcal{T}
$$
-Symmetric Quantum Mechanics, Phys. Lett. A 328, 102–9 (2004)
5. Bender, C.M., Brod, J., Refig, A.T., Reuter, M.E.: The
$$
\mathcal{C}
$$
Operator in
$$
\mathcal{P}\mathcal{T}
$$
-Symmetric Quantum Theories, J. Phys. A: Math. Gen. 37, 10139–10165 (2004)