Taxation of pensions and annuities limited to the resident state, with annuity defined by periodic payments for consideration. Pensions and remuneration for past employment paid to a resident are taxable only in that resident State, subject to paragraph (2) of Article 19; annuities payable to a resident are similarly taxable only in the resident State. 'Annuity' means a stated sum payable periodically during life or a specified period in return for adequate and full consideration in money or money's worth.