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Fotothek df tg Geometrie Mathematik Gedchtniskunst Mnemotechnik Mnemonik. Scan Deutsche Fotothek dftg color MIKCenter Berlin GmbH Frankfurt Main Mnemotechnische Assoziationstechnik ZahlenSymbolSystem Papier Kupferstich cm Geometrie Mathematik Gedchtniskunst Mnemotechnik Mnemonik ppn Druck Deutsche Fotothek gefrdert von