Interesting and important for police-car-freaks:
http://www.amazon.de/Deutsche-Polizeifahrzeuge-Frank-Schwede/dp/3613020807

Once I've looked inside the book. It's obviosly made very exactly

About police-cars from over the whole world:
http://www.sachbuchwelt.de/product_info.php?info=p8144_Polizeifahrzeuge---aus-aller-Welt.html

O.k., these books are written in German, but the pics and the technical informations should be interesting for non-German-speakers, too.

Shall I look for someone over here for the books or the quartett? No problem for me, when I'll visit the next oldtimer-markets.