* {{cite book | last=Wolf | first=Mechthild | title=Immer eine Idee besser | publisher=Degussa AG | publication-place=Frankfurt am Main | date=1998 | isbn=3-00-002389-5 | language=de}}
<ref name="p366">{{cite book | last=Wolf | first=Mechthild | title=Immer eine Idee besser | publisher=Degussa AG | publication-place=Frankfurt am Main | date=1998 | isbn=3-00-002389-5 | language=de | page=}}</ref>