Keywords: Soft abacus, Japan - Ridai Museum of Modern Science, Tokyo - DSC07475.JPG en Exhibit in the Ridai Museum of Modern Science Tokyo University of Science Kagurazaka campus - 1-3 Kagurazaka Shinjuku-ku Tokyo 2015-02-20 01 53 48 own Daderot other versions cc-zero Abaci in the Ridai Museum of Modern Science |