Keynes spent a tremendous amount of time and energy attempting to tutor Harrod on the mechanics of his IS-LM model between July to September, 1935. Keynes's painstaking slow attempts finally led Keynes in desperation to write a three point postscript to his letter of August, 1935, that is...

Keynes told Hicks very clearly on March 31st, 1937 that Keynes had already done what Hicks had done on page 156 of his 1937 Econometrica paper, which was to add Aggregate Actual Income I (Keynes's Y) into the three equation set comprising Hicks's later version of Keynes's IS-LM model. However,...