2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/63022Talk at the International Conference ``Géométrie au vingtième ciècle: 1930--2000'', Paris, Institut Henri Poincaré, Sept. 2001. The title is a homage to Hans Rademacher and Otto Toeplitz whose book fascinated the author many years ago.27 pp., amstex file, no figures. This version contains minor corrections and revisionsAlgebraic Geometrytext