I'd like to thank Alex Hagen-Zanker, Christopher Kormanyos, Conrad Poelman, Eugene Yakubovich, Giovanni Piero Deretta, Hartmut Kaiser, Jeffrey Lee Hellrung, Nat Goodspeed, Robert Stewart, Vicente J. Botet Escriba and Yuriy Krasnoschek.

Especially Eugene Yakubovich, Giovanni Piero Deretta and Vicente J. Botet Escriba contributed many good ideas during the review.