1. R G Sachs, Phys. Rev. 126, 2256 (1962)
2. European Muon Collaboration: J Ashman et al, Phys. Lett. B206, 364 (1988); European Muon Collaboration: J Ashman et al, Nucl. Phys. B328, 1 (1989)
3. J J Kelly, Phys. Rev. C66, 065203 (2002) J Friedrich and T Walcher, Eur. Phys. J. A17, 607 (2003)
4. S L Glashow, Physica (Amsterdam) 96A, 27 (1979)
5. The LEGS Collaboration: G Blanpied et al, Phys. Rev. Lett. 79, 4337 (1997) R Beck et al, Phys. Rev. Lett. 78, 606 (1997); Phys. Rev. C64, 025203 (2001)