Alexander's Hetaroi
Deity
I do think if there are instances where there are fewer than 3 copies, such as only 2, you would only need both with an Industry on one. That's according to the wiki so nothing to do with a mod.Curiously, in my current game, I could suddenly build Corporations on resources I only had 2 of, which were the only 2 existing of those resources in the world (i.e. I controlled 2/2 of those resources). I reckon perhaps some mod allowed this without me being aware.