Towards the Event Horizon - The Vicinity of AGN at Micro-Arcsecond Resolution by Krichbaum, T, Graham, D, Alef, W, Kraus, A, Sohn, B, Bach, U, Polatidis, A, Witzel, A, Zensus, J, Bremer, M, Greve, A, Grewing, M, Doeleman, S, Phillips, R, Rogers, A, Fagg, H, Strittmatter, P, Ziurys, L, Conway, J, Booth, R, Urpo, S