Schafer, J. B., Frankowski, D., Herlocker, J. & Sen, S. (2007). Collaborative Filtering Recommender Systems. In P. Brusilovsky, A. Kobsa & W. Nejdl (ed.), The Adaptive Web: Methods and Strategies of Web Personalization , Vol. 4321 (pp. 291-324) . Springer . ISBN: 978-3-540-72078-2.