Kirby co-plot credit was acknowledged by Lee and Kirby in several interviews. The credit here read "Why are Stan (The Man) Lee and Jack (King) Kirby the most honored creative team in all of comicdom?"
Letters from: Mark McCaffery, Michael Grecsek, Don Sampson, Jeff Stasi, Dale Miller, Lane Bailey, and Dana Smith & Chris Dunny; M.M.M.S. membership form.