Kathy Sierra was a co-developer of the SCJP and SCEA exams. Kathy was a master trainer for Sun Educational Services, where she taught Java instructors. She is the sole founder of the world's largest Java certification web site, Javaranch.com. Kathy worked for Sun Educational Services in the course development, customer training, and certification departments. Bert Bates is an SCJP and OCP and has been developing software for the last 30 years. He participated in the development of the OCP, OCA, SCJP, SCEA, SCWCD, SCBCD, SCMAD, and SCWSD exams. Bert has been teaching software development, including Java programming, for many years. Elisabeth Robson has an MSc in Computer Science and was a software programmer and engineering manager at The Walt Disney Company for many years. Since 2012 she has been a freelance writer and instructor. She produces online training and has written four best-selling books.