* {{cite book | last=Gujer | first=Eric | title=Kampf an neuen Fronten | publisher=Campus Verlag | publication-place=Frankfurt am Main New York, NY | date=2006 | isbn=978-3-593-37785-8 | language=de}}
<ref name="e841">{{cite book | last=Gujer | first=Eric | title=Kampf an neuen Fronten | publisher=Campus Verlag | publication-place=Frankfurt am Main New York, NY | date=2006 | isbn=978-3-593-37785-8 | language=de | page=}}</ref>