Independent Personal Services
(1) Income derived by a resident of a Contracting State in respect of professional services or other similar activities of an independent character shall be taxable only in that State unless he has a fixed base regularly available to him in the other Contracting State for the purpose of performing his activities. If he has such a fixed base, the income may be taxed in the other State but only so much of it as is attributable to that fixed base.
(2) The term "professional services" includes especially independent scientific, literary, artistic, educational or teaching activities as well as the independent activities of physicians, lawyers, engineers, dentists, architects, auditors, and accountants.
(3) Notwithstanding the provisions of paragraph (1) income derived by a resident of a Contracting State in respect of professional services or other activities of an independent character, shall be taxable in the other Contracting State, if the individual is present in the other State for a period or periods exceeding in the aggregate 183 days in any 12 month period commencing or ending in the fiscal year concerned even if no fixed base available to him for the provision of services or conduct of activities, but only so much/thereof as is attributable to services performed in that other State.