Independent Personal Services
(1) Income derived by a resident of a Contracting State from professional services or other activities of an independent nature shall be taxable only in that Contracting State. However, such income may be taxed in the other Contracting State if the resident 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 Contracting State but only so much of it as is attributable to that fixed base.
(2) The term "professional services" includes in particular, independent scientific, literary, educational or teaching activities, as well as the independent activities of physicians, lawyers, engineers, architects, dentists and accountants.