Coherence loss in phase-referenced VLBI observations I. Martí-Vidal, E. Ros, M. A. Pérez-Torres, J. C. Guirado, S. Jiménez-Monferrer and J. M. Marcaide A&A, 515 (2010) A53 Published online: 09 June 2010 DOI: 10.1051/0004-6361/201014203