Galaxy structures - Groups, clusters and superclusters
  We provide a brief summary of the history of galaxy structure studies. We
also introduce several large-scale redshift surveys and summarize the most
commonly used methods to identify the groups and clusters of galaxies. We
present several catalogues of galaxy groups.These catalogues can be used to
study the galaxy groups in different environments. We also consider the
properties of superclusters of galaxies in the nearby Universe and describe the
largest system of galaxies observed - the Sloan Great Wall.
