1. Yu. A. Gol’fand and E. P. Likhtman, Pis’ma Zh. Eksp. Teor. Fiz. 13, 452 (1971) [JETP Lett. 13, 323 (1971)].
2. W. Rarita and J. S. Schwinger, Phys. Rev. 60, 61 (1941).
3. V. Bargmann and E. P. Wigner, Proc. Nat. Acad. Sci. USA 34, 211 (1948).
4. V. I. Ogievetskii and I. V. Polubarinov, Yad. Fiz. 4, 216 (1966) [Sov. J. Nucl. Phys. 4, 156 (1966)].
5. M. V. Chizhov and G. Dvali, arXiv:0908.0924[hep-ph].