1. http://isotc213.ds.dk – Home page of ISO/TC 213.
2. Chain of Standards: A New Concept in Tolerancing and Engineering Drawing GPS-Standards;Bennich,1993
3. Geometrical Dimensioning and Tolerancing for Design Manufacturing and Inspection;Henzold,2006
4. Geometrical Product Specifications—Course for Technical Universities;Bialas,2001
5. http://www.cen.eu.