Statistical properties and universality in earthquake and solar flare occurrence L. de Arcangelis, E. Lippiello, C. Godano and M. Nicodemi Eur. Phys. J. B, 64 3-4 (2008) 551-555 Published online: 08 February 2008 DOI: 10.1140/epjb/e2008-00057-5