Carlos Delgado Kloos, Denis Gillet, Raquel M. Crespo García, Fridolin Wild, Martin Wolpers: Towards Ubiquitous Learning - 6th European Conference of Technology Enhanced Learning, EC-TEL 2011, Palermo, Italy, September 20-23, 2011. Proceedings. Lecture Notes in Computer Science 6964, Springer 2011, ISBN 978-3-642-23984-7