Yang Zhang Jing Zhao Guohong Cao Roadcast: A Popularity Aware Content Sharing Scheme in VANETs. 223-230 2009 ICDCS http://dx.doi.org/10.1109/ICDCS.2009.19 conf/icdcs/2009 db/conf/icdcs/icdcs2009.html#ZhangZC09