I’ve been meaning to get this set up for quite a while, and now that I actually have some solid sources (all secondary for now), I am able to put this together.
Zotero is a great bibliography tool, and the web version allows anyone to collaborate on a group bibliography. This will be helpful in working with the Concentration Camp Memorial and Documentation Center of Porta Westfalica (CCMDC), a group that is actively working with the city of Porta Westfalica to put up memorial signs and collect information relating to the former labor camps.
The Zotero bibliography is located here: https://www.zotero.org/groups/nazi_tunnels/items
The CCMDC does not yet have their own website, I’ll have to see if I can fix that.