Mikael Lindvall Dirk Muthig Aldo Dagnino Christina Wallin Michael Stupperich David Kiefer John May Tuomo Kähkönen 26-34 2004 37 IEEE Computer 12 http://doi.ieeecomputersociety.org/10.1109/MC.2004.231 db/journals/computer/computer37.html#LindvallMDWSKMK04