Wellfoundedness proofs by means of non-monotonic inductive definitions II: first order operators
Toshiyasu Arai · arXiv (Cornell University) · 2010
In this paper, we give two proofs of the wellfoundedness of recursive notation systems for $Π_N$-reflecting ordinals. One is based on $Π_{N-1}^0$-inductive definitions, and the other is based on distinguished classes.