?url_ver=Z39.88-2004&rft_id=doi%3A10.1016%2Fj.econlet.2010.03.005&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.aufirst=Ennio&rft.aulast=Bilancini&rft.au=Bilancini%2C+Ennio&rft.date=2010&rft.atitle=Preferences+and+normal+goods%3A+An+easy-to-check+necessary+and+sufficient+condition&rft.title=Economics+Letters&rft.issue=1&rft.pages=13-15&rft.volume=108&rft.issn=0165-1765&rft.genre=article