The trion: two electrons plus one hole versus one electron plus one exciton M. Combescot, O. Betbeder-Matibet and F. Dubin Eur. Phys. J. B, 42 1 (2004) 63-83 Published online: 26 November 2004 DOI: 10.1140/epjb/e2004-00358-7