1. Aslan, D. and Aktaş Arnas, Y. 3–6 Yaş Grubu Çocuklarda Geometrik Düşüncenin Gelişimi [The development of geometrical thinking in a three‐ to six‐year‐old children’s group]. paper presented at the1st International Pre‐school Education Conference. June, Istanbul, Turkey.
2. Characterizing the van Hiele Levels of Development in Geometry