1. A. Giuliani, Acta Phys. Pol. B 41, 1447 (2010)
2. C. Nones, Nuovo Cimento B 125(4), 417 (2010)
3. C. Bucci, P. Gorla, W. Seidel, (2011). arXiv:1103.5296v1
4. J.W. Beeman et al., (2011). arXiv:1106.6286
5. J. Schnagl et al., Nucl. Instrum. Methods Phys. Res. A 444, 245 (2000)