Optical astrometric positions of 59 northern ICRF radio sources M. Assafin, D. A. Nedelcu, O. Badescu, P. Popescu, A. H. Andrei, J. I. B. Camargo, D. N. da Silva Neto and R. Vieira Martins A&A, 476 2 (2007) 989-993 Published online: 09 October 2007 DOI: 10.1051/0004-6361:20078441