## References 

[1] C M Bender and S Boettcher, Phys. Rev. Lett. 80 (1998) 5243 

[2] C M Bender, S Boettcher and P N Meisinger, J. Math. Phys. 40 (1999) 2201 

[3] C M Bender et al., Phys Rev D 74 (2006) 025016 

[4] H F Jones and J Mateo, Phys Rev D 73 (2006) 085002 

[5] Y Ben-Aryeh and R Barak, Phys Lett A 351 (2006) 388 

[6] B Bagchi, F Cannata and C Quesne, Phys. Lett. A 269 (2000) 79 

[7] M Znojil, Phys. Lett. A 259 (1999) 220 

[8] Z Ahmed, Phys. Lett. A 287 (2001) 295 

[9] Z Ahmed, Phys. Lett. A 290 (2001)19 

[10] A Khare and B P Mandal, Phys. Lett. A 272 (2000) 53 

[11] Andrianov A A, Ioffe M V, Cannata F and Dedonder J P (1999) Int. J. Mod. Phys. A14 2675 

[12] V Buslaev and V Grecchi, J. Phys. A : Math. Gen. 26 (1993) 5541 

[13] M Znojil and G L´evai, Phys. Lett. A 271 (2000) 327 

[14] B Bagchi, S Mallik, C Quesne and R Roychoudhury, Phys. Lett. A 289 (2001) 34 

[15] P Dorey, C Dunning and R Tateo, J. Phys. A : Math. Gen. 34 (2001) 5679 

[16] R Kretschmer and L Szymanowski, Czech. J.Phys 54 (2004) 71 

