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Peter Øhrstrøm , Per F. V. Hasle , Ulrik Sandborg-Petersen (2012) Synthese 188 (3).
Prior's defence of Hintikka's theorem
a discussion of prior's "the logic of obligation and the obligations of the logician"
Peter Øhrstrøm , Jörg Zeller, Ulrik Sandborg-Petersen
pp. 449-454
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