Dr Andrew Butterfield holds an honours degree in Engineering and a PhD in Computer Science and is currently Head of the Foundation and Methods Group at Trinity College Dublin, as well as Director of Undergraduate Teaching and Learning in the School of Computer Science and Statistics. His research interests include the formal aspects of computing and pure lazy functional programming languages, and he has published in various specialist journals (Formal Aspects of Computing, Science of Programming), has edited a number of conference proceedings (Implementing Functional Languages, Unifying Theories of Programming) and has been guest editor for an issue of Formal Methods in System Design. Dr John Szymanski is a lecturer at the University of York. He has written many journal articles as well as a tutorial guide in electronics called Basic Mathematics for Electronics Engineers: Models and Applications (Van Nostrand Reinhold, 1989).