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Michael H. G. Hoffmann, Johannes Lenhard , Falk Seeger (2005) Activity and sign: grounding mathematics education, Dordrecht, Springer.
Michael H. G. Hoffmann, Johannes Lenhard , Falk Seeger (2005) Activity and sign: grounding mathematics education, Dordrecht, Springer.
pp. 275-285
This document is unfortunately not available for download at the moment.