Lots of people helped make these experiments possible. First and foremost, my thanks goes to the anonymous participants. They willingly put up with strange programs and strange problems to solve. My former PhD students, Lutz Prechelt, Michael Philippsen, and Barbara Unger, deserve the credit for making up and testing the programs and maintenance tasks, and collecting and analyzing the data. Thanks also go to Ernst Denert and Peter Brössler for encouraging sd&m engineers to participate. Lawrence Votta helped with experimental design. Marek Vokac, Dag Sjoberg, Erik Arisholm, and Magne Aldrin of Simula Labs provided the programming environment for monitoring participants. Marek Vokac did most of the analysis work at Simula. Dag Sjoberg had the (at the time radical) idea of paying consultants for participating in experiments; he also acquired the funding to do so.