English: Taken from Patricio G. Herbst, "Establishing a Custom of Proving in American School Geometry: Evolution of the Two-Column Proof in the Early Twentieth Century", Educational Studies in Mathematics, Vol. 49, No. 3 (2002), pp. 283-312. Herbst says, "Photographed by the author from Schulze and Sevenoak, 1913, p. 53, Macmillan publishers."
This paper is available from https://www.jstor.org/stable/3483034
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2008-10-05 20:37 CBM 437×404× (159952 bytes) {{PD-us}} == Source == Taken from Patricio G. Herbst, "Establishing a Custom of Proving in American School Geometry: Evolution of the Two-Column Proof in the Early Twentieth Century", ''Educational Studies in Mathematics'', Vol. 49, No. 3 (2002), pp. 28
{{BotMoveToCommons|en.wikipedia|year={{subst:CURRENTYEAR}}|month={{subst:CURRENTMONTHNAME}}|day={{subst:CURRENTDAY}}}} {{Information |Description={{en|Taken from Patricio G. Herbst, "Establishing a Custom of Proving in American School Geometry: Evolution