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

Akim Demaille
Christian Dax
Étienne Renault
Felix Klaedtke
František Blahoudek
Gerard J. Holzmann
Heikki Tauriainen
Jean-Michel Couvreur
Jean-Michel Ilié
Joachim Klein
Kristin Y. Rozier
Martin Dieguez Lodeiro
Michael Weber
Nikos Gorogiannis
Rüdiger Ehlers
Silien Hong
Sonali Dutta
Tomáš Babiak
Yann Thierry-Mieg