qnli question: Lionel Robbins' The Great Depression was a result of his support for what? sentence: 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.