Independent personal services taxation follows residence, with source-state taxation limited by fixed base and day-count exceptions. Income from professional services or other independent activities is taxable only in the resident State unless the services are performed through a fixed base in the other Contracting State or the individual stays there for at least 183 days in the relevant twelve-month period. In those cases, the other State may tax only the income attributable to the fixed base or to activities carried on there. Professional services include independent scientific, literary, artistic, educational or teaching work, and the independent activities of physicians, lawyers, engineers, architects, dentists and accountants.