Multiwavelength VLBI observations of Sagittarius A* R.-S. Lu, T. P. Krichbaum, A. Eckart, S. König, D. Kunneriath, G. Witzel, A. Witzel and J. A. Zensus A&A, 525 (2011) A76 Published online: 02 December 2010 DOI: 10.1051/0004-6361/200913807