Shortened footnote and citation:
{{sfn | Lau | 2007 | p=}}
* {{cite book | last=Lau | first=Dietlinde | title=Algebra und Diskrete Mathematik | publisher=Springer Verlag | publication-place=Berlin Heidelberg | date=2007 | isbn=3-540-72364-1 | language=de}}
Named reference:
<ref name="e642">{{cite book | last=Lau | first=Dietlinde | title=Algebra und Diskrete Mathematik | publisher=Springer Verlag | publication-place=Berlin Heidelberg | date=2007 | isbn=3-540-72364-1 | language=de | page=}}</ref>