Equivalence of Tucker's Lemma and the No-Antipodal-Extension Form of the Borsuk-Ulam Theorem Combinatorics Index and Cohomological Index of the Antipodal Sphere Combinatorics Duals of Transversal Matroids Discrete Mathematics Uniqueness of Countable Atomic Models Logic Principal Form of a Group Isotope Combinatorics Asymmetric Plünnecke Inequality Combinatorics Partition Matroids Are Matroids Combinatorics Tutte One-Factor Theorem Combinatorics Discrete Mathematics Area Combinatorics Subarea