@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}
}
@book {KorBraBenKruLadVog-EML-2014,
	title = {Early Mathematics Learning},
	year = {2014},
	publisher = {Springer-Verlag},
	organization = {Springer-Verlag},
	keywords = {submitted},
	isbn = {978-1-4614-4677-4},
	url = {http://www.springer.com/education+\%26+language/mathematics+education/book/978-1-4614-4677-4},
	editor = {Ulrich Kortenkamp and Birgit Brandt and Christiane Benz and G{\"o}tz Krummheuer and Silke Ladel and Rose Vogel}
}
@inbook {LadKor-DTBLEPVUAAT-2013,
	title = {Designing a technology based learning environment for place value using artifact-centric activity theory},
	booktitle = {Proceedings of the 37th conference of the International Group for the Psychology of Mathematics Education. Mathematics learning across the life span},
	volume = {1},
	year = {2013},
	pages = {188-192},
	keywords = {refereed},
	author = {Silke Ladel and Ulrich Kortenkamp},
	editor = {Anke M. Lindmeier and Aiso Heinze}
}
