That's it? Duke couldn't find any more than that?
This article only focuses on companies located in Pennsylvania.
For companies located elsewhere, you'll have to look-up the full report from Duke University.
Yes, I knew that; in fact, I had originally had some sentences along the lines of
"Pennsylvania was once one of our great manufacturing states, and now this all that we can find? Several of those smaller companies even only do parts that might be used by rail companies."