A catalog of secondary photometric standard stars around gravitational lenses Th. Nakos, E. O. Ofek, P. Boumis, J. Cuypers, D. Sinachopoulos, E. van Dessel, A. Gal-Yam and J. Papamastorakis A&A, 402 3 (2003) 1157-1158 Published online: 23 April 2003 DOI: 10.1051/0004-6361:20030310