Rasiowa-Sikorski Lemma Set Theory Type Existence Theorem by Compactness Logic Basic Type-Counting Criterion for Stability Logic Evaluation of Check Names and the Generic Name Set Theory Correctness of the Cycle-Canceling Algorithm Combinatorics Informal Main Gap Principle Logic Integral Flow Theorem Combinatorics Bogolyubov Lemma for Finite Vector Spaces Combinatorics Discrete Mathematics Area Combinatorics Subarea