Clopen Basis Theorem for Type Spaces Logic Church's Theorem on Undecidability of First-Order Validity Logic Circuit Axioms Characterize Matroids Discrete Mathematics Lovász Extension Convexity Criterion Combinatorics Quantifier Elimination Determines Complete Types from Quantifier-Free Types Logic Sperner's Lemma Combinatorics Stability Hierarchy for Countable Theories Logic Regular Grammars Produce Nondeterministic Automata Discrete Mathematics Discrete Mathematics Area Combinatorics Subarea