Hayek continued his research on monetary and capital theory, revising his theories of the relations between credit cycles and capital structure in Profits, Interest and Investment (1939) and The Pure Theory of Capital (1941), but his reputation as an economic theorist had by then fallen so much that those works were largely ignored, except for scathing critiques by Nicholas Kaldor. Lionel Robbins himself, who had embraced the Austrian theory of the business cycle in The Great Depression (1934), later regretted having written the book and accepted many of the Keynesian counter-arguments.