The Margaret Thatcher Foundation has release hundreds of documents related to the Hayek – Thatcher relationship. Here is a letter from Thatcher to Hayek dated May 18, 1979.
Hayek’s equilibrium theory offered a wealth of suggestions that were to be taken up in the literature of the 1940s and 1950s. The idea of intertemporal equilibrium, which was to be precisely defined in axiomatic terms by Arrow and Debreu, took shape in his writings of the 1920s and 1930s. — Bruna Ingrao & Giorgio Israel