I want to know the answer to the following question:
In which year did Popper write Hayek a letter expressing his intellectual debt to him?
All the background I'm provided with is that "While there is some dispute as to the matter of influence, Popper had a long-standing and close friendship with economist Friedrich Hayek, who was also brought to the London School of Economics from Vienna.". Is that enough to answer the question?
Answer: no