Campbell sources
Yup, I just saw that you had made the changes.  I've been trying to find some sources for the last couple of days but couldn't.  I can't remember if I was the guy who put in the "pen in the hand of Campbell" or not.  I definitely read that somewhere years ago.  Then when I had lunch with Heinlein back in the early 80s I asked him about it and he was not happy with the concept, hehe.  So, unfortunately, that falls under Original Research, I guess.  I encountered a similar problem with other comments that I put into the Heinlein article.... Wish I could source this.