ARTICLE 14
Independent Personal Services
(1) Income derived by a resident of a Contracting State in respect of professional services or other independent activities of a similar 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, only so much of the income as is attributable to that fixed base may be taxed in the other State.
(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, architects and dentists.