Further evidence for low-energy protonium production in vacuum E. Lodi Rizzini, L. Venturelli, N. Zurlo, M. Charlton, C. Amsler, G. Bonomi, C. Canali, C. Carraro, A. Fontana, P. Genova et al. (13 more) Eur. Phys. J. Plus, 127 10 (2012) 124 Published online: 10 October 2012 DOI: 10.1140/epjp/i2012-12124-9