ARTICLE 14
Independent Personal Services
(1) Income derived by an individual who is a resident of a Contracting State in respect of professional services or other activities of an independent character shall be taxable only in that Contracting 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 or had such a fixed base, the income may be taxed in the other Contracting 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, architects, dentists and accountants.