Task: Question Generation
Input (English): After editing a book on John Stuart Mill's letters he planned to publish two books on the liberal order, The Constitution of Liberty and "The Creative Powers of a Free Civilization" (eventually the title for the second chapter of The Constitution of Liberty). He completed The Constitution of Liberty in May 1959, with publication in February 1960. Hayek was concerned "with that condition of men in which coercion of some by others is reduced as much as is possible in society". Hayek was disappointed that the book did not receive the same enthusiastic general reception as The Road to Serfdom had sixteen years before.
Output (English): As of the release of his 1960 book, how long had it been since The Road to Serfdom was released?