?url_ver=Z39.88-2004&rft_id=10.1006%2Fjcss.1999.1636&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.aufirst=Flavio&rft.aulast=Corradini&rft.au=Corradini%2C+Flavio&rft.issue=3&rft.pages=412-449&rft.volume=59&rft.date=1999&rft.atitle=Models+of+Nondeterministic+Regular+Expressions&rft.title=Journal+of+Computer+and+System+Sciences&rft.issn=0022-0000&rft.genre=article