Our thanks to the following people for their help:

Yuliya Babenko, Vladislav Babenko, Borislav Bojanov, Yuri Brudnyi, Martin Buhmann, Paul Butzer, Tamás Erdélyi, Jürgen Garloff, Leonid Golinskii, Zvi Har'El, Ewa Hensz-Chadzynska, Tom Hogan, Olga Holtz, Graham Jameson, Ken Lord, Joerg Liesen, Paul Nevai, Gerhard Opfer, Pencho Petrushev, Christophe Rabut, Heinz-Joachim Rack, Szilárd Révész, Ed Saff, Robert Schaback, Alexei Shadrin, Igor Shevchuck, Shimon Sobol, Dennis Stanton, Karl-Georg Steffens, József Szabados, Walter Van Assche, Jiri Veselý, Shayne Waldron, and Antonella Zanna.