Lexicographic Product of Well-Orders Logic Furstenberg Correspondence Principle Combinatorics Admissibility of Existential Elimination Under the Eigenvariable Condition Logic Uniqueness of the Irreducible Automaton Discrete Mathematics Definable Types Have Global Invariant Extensions Logic Transitivity of Many-One Reducibility Logic Hausdorffness of Type Spaces Logic Uniqueness of Order Isomorphisms Between Well-Orders Logic Discrete Mathematics Area Combinatorics Subarea