E. Baykan, M. Henzinger, L. Marian, and I. Weber. WWW '09: Proceedings of the 18th international conference on World wide web, page 1109--1110. New York, NY, USA, ACM, (2009)
M. Shafiei, and E. Milios. ICDM '06: Proceedings of the Sixth International Conference on Data Mining, page 542--551. Washington, DC, USA, IEEE Computer Society, (2006)