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jstor.org
Gibbard, Allan (1993). E. Villanueva (ed.). "Reply to Railton". Naturalism and Normativity. 4. Atascadero, CA: Ridgeview: Ridgeview Publishing Company: 52–59. doi:10.2307/1522826. JSTOR1522826.
loc.gov
lccn.loc.gov
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