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(Note: In Section 3.3 Other approaches, this paper misrepresents Homeier’s approach as being unable to do rule inductions satisfactorily. This is incorrect: he proves and uses “height-based” rule induction principles that give the same sort of ease-of-use as his height-based structural principles.)
let-expressions in proof. Proceedings of TPHOLs, Oxford, 2005. LNCS 3603, pp397–408. (BibTeX) (Slides)