Books on Amazon
Nominator / Prior: should speak of things where sentences containing them can be said to be true - e.g. lp for that p - Then the sentence: T lp (it is true that ...)
Operator / Prior: f only forms sentences from names - ((s) something f s, different from equivalence: forming sentences out of sentences). - Prior: N can not have names as arguments.
Objects of thought Oxford 1971
Arthur N. Prior
Papers on Time and Tense 2nd Edition Oxford 2003