Amela Karahasanovic Petter Bae Brandtzæg Jan Heim Marika Lüders Lotte Vermeir Jo Pierson Bram Lievens Jeroen Vanattenhoven Greet Jans Co-creation and user-generated content-elderly people's user requirements. 655-678 2009 25 Computers in Human Behavior 3 http://dx.doi.org/10.1016/j.chb.2008.08.012 db/journals/chb/chb25.html#KarahasanovicBHLVPLVJ09