This book was mainly written while I stayed at the Catholic University of Louvain. Professor Anton P. Barten was the one who did not only give me a warm welcome in Louvain, but also supported my research with most valuable comments and constructive criticisms. In addition I benefitted from dis cussions with Erik Schokkaert, Denis de Crombrugghe and Jo Baras on various subjects, such as the small-sample correction of Chapter 9. The arduous task of transferring my neat handwriting into a readable typescript was excellently taken care of by Brs. E. Crabbe and notably Brs. F. Duij sens, even...