P. Vorst, and A. Zell. Proceedings of the IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2009), page 395--401. St. Louis, Missouri, USA, (October 2009)
K. Rohweder, P. Vorst, and A. Zell. Proceedings of the 4th European Conference on Mobile Robots (ECMR 2009), page 247--252. Mlini/Dubrovnik, Croatia, (September 2009)