K. Bollacker, C. Evans, P. Paritosh, T. Sturge, and J. Taylor. SIGMOD '08: Proceedings of the 2008 ACM SIGMOD international conference on Management of data, page 1247--1250. New York, NY, USA, ACM, (2008)
S. Auer, M. Weidl, J. Lehmann, A. Zaveri, and K. Choi. Proceedings of the 9th International Semantic Web Conference (ISWC 2010), Berlin/Heidelberg, Springer, (2010)
M. Knuth, N. Ludwig, L. Wolf, and H. Sack. Proceedings of The Second International Workshop on Mining Ubiquitous and Social Environments (MUSE 2011), page 43--53. Athens, Greece, (September 2011)