Difference sets connecting algebra, combinatorics and geometry

Difference sets > Combinatorial geometry > Combinatorics -- Designs and configurations -- Difference sets (number-theoretic, group-theoretic, etc.) > Combinatorics -- Designs and configurations -- Matrices (incidence, Hadamard, etc.) > Combinatorics -- Designs and configurations -- Finite geometries > Number theory -- Algebraic number theory: global fields -- Algebraic numbers; rings of algebraic integers > Group theory and generalizations -- Representation theory of groups -- Ordinary representations and characters > Geometry -- Finite geometry and special incidence structures -- Affine and projective planes > Kombinatorische Geometrie > Differenzmenge