"A Study of the Longitudinal Kink Modes of the String", Phys. Rev. D 13, 2364 (1976). [5] C. Bender, "Introduction to PT-Symmetric Quantum Theory", Contemp. Phys. 46 (2005) 277, arXix:quant-ph/0501052; "Making sense of non-Hermitian Hamiltonian", Rept. Prog. Phys. 70 (2007) 947, arXiv:hep-th/0703096.