Coherence loss in phase-referenced VLBI observations (Corrigendum)I. Martí-Vidal, E. Ros, M. A. Pérez-Torres, J. C. Guirado, S. Jiménez-Monferrer and J. M. MarcaideA&A, 533 (2011) C1DOI: https://doi.org/10.1051/0004-6361/201014203e