Towards the Event Horizon - The Vicinity of AGN at Micro-Arcsecond   Resolution
  We summarize the present status of VLBI experiments at 3 mm (86 GHz), 2 mm (129-150 GHz) and 1.3 mm (215-230 GHz). We present and discuss a new 3 mm VLBI map of M87 (Virgo A), which has a spatial resolution of only approx. 20 Schwarzschild radii. We discuss recent VLBI results for SgrA* and argue in favor of new observations within an extended European mm-VLBI network, in order to search for variability. We discuss the possibilities to image the `event horizon' of a super-massive black hole at wavelengths < 2mm, and conclude that the addition of large and sensitive millimetre telescopes such as CARMA, the SMA, the LMT and ALMA will be crucial for this. 
T.P. Krichbaum, D.A. Graham, W. Alef, A. Kraus, B.W. Sohn, U. Bach, A.   Polatidis, A. Witzel, J.A. Zensus, M. Bremer, A. Gr...