https://sites.google.com/view/werkgroep-mecanotelie/homepage

https://en.wikibooks.org/wiki/International_Postage_Meter_Stamp_Catalog

http://www.meterfranking.co.uk/

http://www.frankeerstempel.nl/index.htm

http://www.fg-freistempel.de/

http://kjell.smult.com/franko_hist_leverant.htm

http://www.belgianphilatelicstudycircle.org.uk/weblinks.htm