Last letter to Hardy Jan. 1920.

His wife lived with him and looked after him during his illness after his return from England. Even during those months of prolonged illness he kept on working, though in a reclining position, at a furious pace and kept jotting down his results on sheets of paper. In his last and only letter to Hardy written after his return to India, in January 1920, Ramanujan communicated his original work on what he called mock theta functions.