Paolo Boldi Roberto Posenato Massimo Santini Sebastiano Vigna Traps and Pitfalls of Topic-Biased PageRank. 107-116 2006 WAW http://dx.doi.org/10.1007/978-3-540-78808-9_10 conf/waw/2006 db/conf/waw/waw2006.html#BoldiPSV06