Karl de Leeuw has been engaged as a lecturer in Information Security at the University of Amsterdam and as an editor of sources about the history and philosophy of mathematics at the University of Utrecht. He has written his Ph. D about the history of cryptology in the Netherlands and has published extensively about this subject in scholarly journals in the U.S. and the U.K. His current research interests include the philosophy and history of science & technology, the history of computer science, and intelligence history; Jan Bergstra is a full professor in Computer Science at the University of Amsterdam. He is a logician by training and has a wide scope of interests. Jan Bergstra is a professor of computer science at the University of Amsterdam, a part time professor of applied logic at Utrecht University (both NL) and he is a honorary visiting professor with the University of Swansea (UK). His main resarch interest has been computability theory, process algebra and abstract data types, but he worked in many other aspects of computer science as well, including in particular decidability problems that arise in the theory of computer virusses. He is a member of the Academia Europaea. He is currently managing editor of 'Science of Computer Programming' and the 'Journal of Logic and Algebraic Programming'.