Selected topical problems of mathematical physics are being dealt with by emphasizing methodical aspects. For this reason also questions regarding mathematical model building are being discussed. The book contains the papers presented at the Conference in Oberwolfach organized by Prof. Dr. B. Brosowski and Prof. Dr. E. Martensen. The contributors are the following renowned mathematicians and physicists: Rainer Kress, Peter Jochum, Miloslav Feistauer, Eberhard Halter, Juergen Scheurle, R.E. Kleinmann/G.F. Roach, Hermann Sohr, Horst Lange, Erik B. Hansen, Rainer Colgen, Johann Baumeister, Zdenek Vlasek, Ulrich Elsaesser, Zdzislaw Domanski, and R. Rautmann.