S. Dulucq, and H. Touzet. Proceedings of the 14th Annual Conference on Combinatorial Pattern Matching, page 83--95. Berlin, Heidelberg, Springer-Verlag, (2003)
D. Parra, and P. Brusilovsky. Proceedings of the Workshop on Web 3.0: Merging Semantic Web and Social Web, volume 467 of CEUR Workshop Proceedings, (June 2009)