Sources and acknowledgments

In addition to those quoted in the text, the author would like to thank Nikolai Ardey, Alexandra Borejko, Thymian Bussemer, Lars Carlsson, Christian Dahlheim, Rüdiger Fleischer, Seth Goldstein, Patrick von Herz, Daniel Kauer, Holger Klein, Kamila Laures, Hazim Nada, Florian Otto, Natasha Santha, Matthias Schmidt, Hauke Stars and Mark Wakefield.