Foreword

During his career, Joe published more than 190 research articles with over 50 different coauthors.Out of these, more than 70 were published after his retirement.His most cited work is the book Spaces of constant curvature from 1967, which has become a classic and is still an excellent timely reference.It is a valuable rich resource for self-study by graduate students and senior researchers interested in the connections between differential geometry and Lie theory.The interplay between geometry and group theory is one of the recurring themes in Joe's work.His research contributions ranged from homogeneous spaces and complex manifolds over both finite-and infinite-dimensional Lie groups to representation theory and harmonic analysis.Joe also was a very dedicated teacher who considered it one of his most important duties to pass on his knowledge to the next generation.He never grew tired of answering questions and did so with extraordinary patience.He supervised 23 PhD students.In the 1990s, his students affectionately referred to their group as the "Wolfpack".