It is not so well known that it [Keynes's and my own move from thinking in terms of price-levels and the rate of interest to thinking in terms of inputs and outputs] is matched by a movement from Hayek to Harrod. I once asked Harrod what had put him on to the construction of his so-call 'dynamic' theory; he said, to my surprise, that it was thinking about Hayek.

p. 340 - Money, Interest and Wages, (1982)