We thank the referee Dr. Marcello Felli for his helpful comments and for taking us on an enlightening tour through the "Orion Radio Zoo". T.L.W., K.J.J. and A.R.T. were supported in part by the Max-Planck-Forschungspreis administered by the Alexander von Humboldt-Stiftung. A.R.T.'s stay at NRL and USNO was supported in part by a grant from the Deutscher Akademischer Austauschdienst. During the work T.L.W. was a G.A. Miller Professor at the University of Illinois.
© European Southern Observatory (ESO) 1997
Online publication: July 3, 1998