Groups of galaxies in the SDSS Data Release 7 - Flux- and volume-limited samplesE. Tago, E. Saar, E. Tempel, J. Einasto, M. Einasto, P. Nurmi and P. HeinämäkiA&A, 514 (2010) A102DOI: https://doi.org/10.1051/0004-6361/200913687