We are grateful to these people for their comments, help, or
suggestions.

Étienne Renault
Gerard J. Holzmann
Heikki Tauriainen
Jean-Michel Couvreur
Jean-Michel Ilié
Kristin Y. Rozier
Martin Dieguez Lodeiro
Michael Weber
Nikos Gorogiannis
Rüdiger Ehlers
Silien Hong
Tomáš Babiak
Yann Thierry-Mieg
