@inbook {LadKor-EML-2014,
	title = {Number concepts {\textendash}- processes of internalization and externalization by the use of multi-touch technology Silke Ladel and Ulrich Kortenkamp},
	booktitle = {Early Mathematics Learning},
	year = {Submitted},
	chapter = {3-3},
	keywords = {ACAT},
	author = {Silke Ladel and Ulrich Kortenkamp}
}
