1. Stoler, P. (ed.): Photopion nuclear physics. New York: Plenum Press 1979
2. Singham, M.K., Tabakin, F.: Ann. Phys. (NY)135, 329 (1980)
3. Cohen, S., Kurath, D.: Nucl. Phys.73, 1 (1965)
4. Hauge, P.S., Maripuu, S.: Phys. Rev. C8, 1609 (1973)
5. Delorme, J., Ericson, M., Figureau, A., Giraud, N.: Phys. Lett.89B, 327 (1980)