Luciano Gamberini Giovanni Petrucci Andrea Spoto Anna Spagnolli Embedded Persuasive Strategies to Obtain Visitors' Data: Comparing Reward and Reciprocity in an Amateur, Knowledge-Based Website. 187-198 2007 conf/persuasive/2007 PERSUASIVE http://dx.doi.org/10.1007/978-3-540-77006-0_24 db/conf/persuasive/persuasive2007.html#GamberiniPSS07