?url_ver=Z39.88-2004&rft_id=10.1371%252Fjournal.pone.0020648&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.aulast=Zhou&rft.au=Zhou%2C+Tao&rft.aufirst=Tao&rft.pages=e20648&rft.issn=1932-6203&rft.title=PloS+One&rft.date=2011&rft.issue=7&rft.volume=6&rft.atitle=Emergence+of+Scale-Free+Leadership+Structure+in+Social+Recommender+Systems&rft.genre=article