M. Becker, J. Mueller, A. Hotho, and G. Stumme. Conference on Pervasive and Ubiquitous Computing Adjunct Publication, page 1175--1182. New York, NY, USA, (2013)
S. Papadopoulos, Y. Kompatsiaris, and A. Vakali. Proceedings of the 12th international conference on Data warehousing and knowledge discovery, page 65--76. Berlin, Heidelberg, Springer-Verlag, (2010)