Francesco Ricci · Lior Rokach · Bracha Shapira · Paul B. Kantor Editors Recommender Systems Handbook 123 Lior Rokach Ben-Gurion University of the Negev Dept. Information Systems Engineering 84105 Beer-Sheva Israel liorrk@bgu.ac.il Paul B. Kantor Rutgers University School of Communication, Information & Library Studies Huntington Street 4 08901-1071 New Brunswick New Jersey SCILS Bldg. USA ISBN 97