info:oai:generic.eprints.org:76info:ofi/fmt:xml:xsd:bookMatsuoYutakaMatsuo, Yutaka <http://www2009.eprints.org/view/author/Matsuo=3AYutaka=3A=3A.html>YamamotoHikaruYamamoto, Hikaru <http://www2009.eprints.org/view/author/Yamamoto=3AHikaru=3A=3A.html>April 2009Community Gravity: Measuring Bidirectional Effects by Trust and Rating on Online Social Networksproceeding