@article{PPN37649882X+dmdlog125, title = {Die Association for the improvement of geometrical teaching.}, booktitle = {Geometrie Bd. 2}, series = {GDML\_Books}, year = {1968}, pages = {232}, url = {http://dml.mathdoc.fr/item/PPN37649882X+dmdlog125} }
(éd.). Die Association for the improvement of geometrical teaching., dans Geometrie Bd. 2, GDML_Books, (1968), p. 232. http://gdmltest.u-ga.fr/item/PPN37649882X+dmdlog125/