Independent personal services: income taxed in resident state unless fixed base or prolonged presence permits taxation abroad. Income of a resident individual from professional or similar independent activities is taxable only in the State of residence except where the individual has a fixed base in the other State, in which case only income attributable to that fixed base may be taxed there, or where the individual's stay in the other State meets the treaty's prolonged presence threshold, in which case only income from activities performed in that other State may be taxed there.