(1) Subject to the provisions of paragraph (2) of Article 20, pensions and other similar remuneration paid to a resident of a Contracting State in consideration of past employment and any annuity paid to such a resident in consideration of past employment shall be taxable only in that State.

(2) The term "annuity" means a stated sum payable periodically at stated times during life or during a specified or ascertainable period of time under an obligation to make the payments in return for adequate and full consideration in money or money's worth.