Three quasi-stellar objects acting as strong gravitational lenses F. Courbin, C. Faure, S. G. Djorgovski, F. Rérat, M. Tewes, G. Meylan, D. Stern, A. Mahabal, T. Boroson, R. Dheeraj and D. Sluse A&A, 540 (2012) A36 Published online: 22 March 2012 DOI: 10.1051/0004-6361/201118015