Benjamin Bercovitz Filip Kaliszan Georgia Koutrika Henry Liou Zahra Mohammadi Zadeh Hector Garcia-Molina CourseRank: a social system for course planning. 1107-1110 2009 SIGMOD Conference http://doi.acm.org/10.1145/1559845.1559994 conf/sigmod/2009 db/conf/sigmod/sigmod2009.html#BercovitzKKLZG09