Across the Space Frontier
I hope this okay to ask this here. A friend of mine is thinking about selling a multiple signed copy of "Across the Space Frontier" by Wernher von Braun, Willey Ley, Fred Whipple, Joseph Kaplan, Heinz Haber, Oscar Schachter. Edited by Cornelius Ryan.
Does anyone know of a good place where I can find out how much this would be worth?
Thanks so much for your help.