We wish to thank the staffs of all the observatories for their contribution to the observations, and to the MPIfR staff for their efforts during the correlation. We thank Dr. R. Schwartz for kindly providing MPIfR VLBI tapes. We also thank Drs. F. Mantovani and A. Alberdi for valuable comments on the manuscript. E.R. acknowledges a fellowship of the Generalitat Valenciana. This work has been partially supported by the Spanish DGICYT grant PB93-0030 and the U.S. National Science Foundation Grant AST89-02087.
© European Southern Observatory (ESO) 1998
Online publication: July 7, 1998