My recent article in the Canadian Encyclopedia discussed the Letters Patent, 1947.
The Letters Patent Constituting the Office of Governor General and Commander-in-Chief of Canada, usually shortened to Letters Patent, 1947, was an edict issued by King George VI that expanded the role of the governor general, allowing him or her to exercise prerogatives of the sovereign. While Letters Patent delegated Crown prerogatives to the governor general, the sovereign remains Head of State.
Click here to read Letters Patent, 1947 in the Canadian Encyclopedia