Glass Chatroom Board

I have spent the last couple of hours looking on-line about Dugan and Northwood, and getting sidetracked looking at some wonderful pieces of glass. On Doty's site it says 'until 1981 carnival glass collectors were unaware of The Dugan glass Company' - that is only 30 years ago, so I can see why books could have the wrong information. I imagine there is still information that could come to light that could change ideas of who made what pieces of glass.
I don't understand the part 'when that Northwood venture was purchased by National Glass' - which venture is this referring to? Lots to learn by me.
Mary