Independent personal services taxable in resident state, unless a fixed base or prolonged presence allows taxation by the other state. Income from independent personal services earned by a resident of a Contracting State is taxable only in that State, except that the other State may tax income attributable to a fixed base regularly available there or income derived from activities performed there when the individual's presence meets a qualifying threshold over a specified period. The exceptions are limited to income attributable to the fixed base or to activities performed during the qualifying presence.