Kiril Borisov Arnaudov is a leading expert in the area of gear design. A native of Bulgaria, Dr. Araudov received his M Sc degree from the Technical University - Sofia, and PhD from the Technical University of Dresden. He has worked in mechanical design, and has served as a Professor and Researcher at the Technical University - Sofia, and the Institute of Mechanics of the Bulgarian Academy of Sciences. He is the author of numerous monographs and technical publications in the area of planetary gear trains, as well as papers for conference proceedings in the field. Dr. Arnaudov is a member of the International Scientific Committee of the "Balkan Journal of Mechanical Transmissions", and a member of the Editorial Board for the journal "Gearing and Transmissions." Dimitar Petkov Karaivanov received his M Sc degree from the Technical University - Sofia, and his PhD from the University of Chemical Technology and Metallurgy - Sofia. Dr. Karaivanov is the author of two monographs, more than 80 scientific publications, and a textbook. He also holds two patents, regitered in Bulgaria. He is a member of the International Scientific Committee of the "Balkan Journal of Mechanical Transmissions," and a member of the editorial board for the journal "Machines, Technologies and Materials." Currently Dr. Karaivanov serves as a Professor (Docent) in Machinery and Machine Elements at the University of Chemical Technology and Metallurgy, Sofia.