Astrometric comparisons of quasar catalogues J. Souchay, S. B. Lambert, A. H. Andrei, S. Bouquillon, C. Barache and C. Le Poncin-Lafitte A&A, 485 1 (2008) 299-302 Published online: 16 April 2008 DOI: 10.1051/0004-6361:20078427