* [https://web.archive.org/web/20110721020749/http://www.poppelsdorf.de/zwischen_melb_und_weiher-Soennecken.htm] Storia dell'azienda relativa a Poppelsdorf | * [https://web.archive.org/web/20110721020749/http://www.poppelsdorf.de/zwischen_melb_und_weiher-Soennecken.htm] Storia dell'azienda relativa a Poppelsdorf |