?url_ver=Z39.88-2004&rft_id=10.1073%2Fpnas.1501444112&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.aufirst=Alexander+M.&rft.aulast=Petersen&rft.au=Petersen%2C+Alexander+M.&rft.issn=1091-6490&rft.issue=34&rft.pages=E4671-E4680&rft.volume=112&rft.date=2015&rft.title=Proceedings+of+the+National+Academy+of+Sciences&rft.atitle=Quantifying+the+impact+of+weak%2C+strong%2C+and+super+ties+in+scientific+careers&rft.genre=article