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Patent:US1218931


Patent:US 1218931
Title:Apparatus for Teaching Arithmetic
Date:13.03.1917
Place:
Country:USA
Person:H. G. Cuthbert
Company:
Internal Links:Lehrmittel
Keywords:
Link to the patent office:
(without guarantee)
 US1218931 (espacenet),  US1218931 (uspto)


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Aus der Patentschrift US1218931