C. Seitz, C. Legat, and J. Neidig. Workshops Proceedings of the 5th International Conference on Intelligent Environments, volume 4 of Ambient Intelligence and Smart Environments, page 51--57. Amsterdam, IOS Press, (2009)
S. Lempert, and A. Pflaum. MMS 2011: Mobile und ubiquitäre Informationssysteme, Kaiserslautern, volume P-185 of GI Edition: Lecture Notes in Informatics (LNI) -- Proceedings, page 53--66. Bonn, Gesellschaft für Informatik, (2011)