Collective excitations of a "gravitationally" self-bound Bose gas S. Giovanazzi, G. Kurizki, I. E. Mazets and S. Stringari Europhys. Lett., 56 1 (2001) 1-7 Published online: 01 December 2003 DOI: 10.1209/epl/i2001-00478-8