REFS references Peter Helm referenzen www.polygraphicum.de WEB ARCHIVES

https://web.archive.org/web/20080601172904/http://www.polygraphicum.de/refs.html

https://web.archive.org/web/20080601172904/http://www.polygraphicum.de/refs.html https://0700polygraf.blogspot.com/2021/06/blog-post_30.html

www.polygraphicum.de