About the authors-- Finn Jensen is an independent consultant in reliability engineering. He received his M.Sc. in Electrical Engineering in 1962 and his Ph.D. in 1970 from the Technical University of Denmark. He has been concerned with practical reliability engineering and research since the early 1970s, forming his own company in 1973. As reliability adviser he has conducted numerous reliability short courses in industry and has published and presented papers at many national and international conferences. Niels Erik Petersen graduated from the Engineering Academy of Denmark in 1976 and specializes in electromechanical engineering. Mr Petersen worked extensively on reliability problems, especially burn-in techniques, before taking up his present position as Development Engineer within a Danish company specializing in heavy industrial machinery.