The following principal investigators were members of the GAP Study Group: H. J. Agostini (Freiburg, Germany), R. Anand (Dallas, TX, USA), J. Arnold (Sydney, Australia), F. Bandello (Udine, Italy), D. S. Boyer (Beverly Hills, CA, USA), D. M. Brown (Houston, TX, USA), D. Callanan (Arlington, TX, USA), U. Chakravarthy (Belfast, Ireland), G. Cowan (Fort Worth, TX, USA), S. Downes (Oxford, United Kingdom), R. Guymer (Melbourne, Australia), L. S. Halperin (Ft. Lauderdale, FL, USA), Y. G. He (Dallas, TX, USA), J. S. Heier (Boston, MA, USA), F. G. Holz (Bonn, Germany), A. Leys (Leuven, Belgium), A. Loewenstein (Tel Aviv, Israel), E. Midena (Padova, Italy), S. Patel (Abilene, TX, USA), D. Pauleikhoff (Münster, Germany), A. Pollack (Rehovot, Israel), C. Pruente/M. Georgopoulus (Vienna, Austria), S. R. Russell (Iowa City, IA, USA), S. V. Sadda (Los Angeles, CA, USA), L. Singerman (Cleveland, OH, USA), J. A. Sahel/S. Mohand-Said (Paris, France), G. Staurenghi (Milan, Italy), M. P. Teske (Salt Lake City, UT, USA), A. Tufail (London, United Kingdom), C. Von Strachwitz (Würzburg, Germany), J. A. Wells III (West Columbia, SC, USA), P. Wiedemann (Leipzig, Germany), and S. Wolf/U. Wolf-Schnurrbusch (Bern, Switzerland).