The properties of isolated Main Galaxies in Sloan Digital Sky Survey   Data Release 3 (SDSS DR3)
  We have constructed a Main galaxy subsample with redshifts in the range 0.08<=z<=0.12 from SDSS Data Release 3 (SDSS DR3), and refer to this subsample as "MGSU"(It contains 67777 galaxies). By cluster analysis, two isolated Main galaxy samples are extracted from this subsample. It turns out that two isolated Main galaxy samples identified at different radii have the same properties. Additionally, we also find that early-type galaxies in isolated Main galaxy samples are fewer than that in close double galaxy sample. 
Deng Xinfa, Ma Xinsheng, Luo Chenghong, Zhang Qun, He Ji-zhou