1. Former Professor and Director of the Institute of Oral Structural Biology, Center of Dental and Oral Medicine and Maxillofacial Surgery, University of Zürich, Switzerland; present address, Grossackerstrasse 38, CH-8152 Opfikon, Switzerland;
2. former Professor of Periodontics and Director of the Microbiology Testing Laboratory, School of Dental Medicine, University of Pennsylvania, USA; present address, 166 Beach Park Boulevard, Foster City, CA 94404, USA;