Author <Equals> "Hopfgartner, Frank" Date Issued <Equals> "2013" Author <Equals> "Larson, Martha" Author <Equals> "Baltrunas, Linas" Subject <Equals> "crowdsourcing" Author <Equals> "Said, Alan" Author <Equals> "Anguera, Xavi" Author <Equals> "Karatzoglou, Alexandros" Subject <Equals> "004 Datenverarbeitung; Informatik" Author <Equals> "Tikk, Domonkos" Author <Equals> "Geurts, Jozef"