At the time, Rolf Pfeifer wasn't there.
https://www.ifi.uzh.ch/en/ailab/group/professors/rolfpfeifer.html

I think this credit in "Understanding intelligenceOctober" (1999) by Rolf Pfeifer and Christian Scheier is the only thing that's left:

"A big thanks goes to Norman Cook of Kansai University and to Paolo Gaudiano of Boston University, and to three anonymous reviewers for their critical reading and their extremely valuable and constructive remarks. Their suggestions have helped improve the text tremendously. Many students from our classes have also supplied us with valuable suggestions. In particular, we thank Marcel Altherr, Natalie Glaus, and Alex Schröder. Isabelle Follath deserves all the credit for the cartoons, without which the book would not be half as much fun. Alex Riegler did a great job in designing the numerous technical illustrations. And last, but not least, a big thanks goes to Eveline Wittmer for managing all the figures."

Always credit the students! 😄