Adelchi Fabrocini (1), Stefano Fantoni (2), Alexey Yu. Illarionov (1 and 3), Kevin E. Schmidt (4). ((1) Dip. di Fisica "E.Fermi", Universita di Pisa, and INFN, Sezione di Pisa; (2) International School for Advanced Studies, SISSA; (3) Joint Institute for Nuclear Research, JINR; (4) Department of Physics and Astronomy, Arizona State University.)
