Groups of galaxies in the SDSS Data Release 7 - Flux- and volume-limited samples E. Tago, E. Saar, E. Tempel, J. Einasto, M. Einasto, P. Nurmi and P. Heinämäki A&A, 514 (2010) A102 Published online: 28 May 2010 DOI: 10.1051/0004-6361/200913687