Before coming to Washington University in 1978, he served on the faculty of the University of Bonn. His areas of specialization are economic theory, especially mathematical economics. Among his articles are: Quantity Guided Pricesetting' (with E. Dierker), Journal of Mathematical Economics, 1988 and Continuous Linear Representability for Binary Relations'' (with W. Trockel), Economic Theory, 1994, Heuristics as Decision Rules --- Part I: The Cobb Douglas Consumer (with W. G�th), Homo Oeconomicus, 2000. His current interests include cooperative game theory and some issues of group learning in contrast to individual learning. He teaches microeconomics at the undergraduate level and graduate level and mathematical methods for graduate students.