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

Akim Demaille
Christian Dax
Ernesto Posse
Étienne Renault
Felix Klaedtke
František Blahoudek
Gerard J. Holzmann
Heikki Tauriainen
Jan Strejček
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