The authors would like to thank the following people for ideas, discussions,
testing and feedback:

Doris Altmann
Johannes Dreesman
Johannes Elias
Marc Geilhufe
Mayeul Kauffmann
Marcos Prates
Barry Rowlingson
Christopher W. Ryan
Klaus Stark
Yann Le Strat
Andr Michael Toschke
Achim Zeileis
