Spectroscopic confirmation of a cluster of galaxies at in the field of the gravitational lens MG 2016+112G. Soucail, J.-P. Kneib, A. O. Jaunsen, J. Hjorth, M. Hattori and T. YamadaA&A, 367 3 (2001) 741-747DOI: https://doi.org/10.1051/0004-6361:20000498