Ladel, S., & Kortenkamp, U..  (2014).  Development of a Flexible Understanding of Place Value. In . Malmö, Schweden: A Mathematics Education Perspective on early Mathematics Learning between the Poles of Instruction and Construction (POEM). Abgerufen von http://www.mah.se/upload/FAKULTETER/LS/LS-seminarier/POEM/Ladel_Kortenkamp%20-%20Development%20of%20a%20flexible%20understanding%20of%20place%20value.pdf