Income from Independent Personal Services
(1) Income derived by a person with permanent residency in a Contracting State from performance of professional services or other activity of an independent character not associated with employment may be taxable only in the other Contracting State only if:
- (a) this person has a fixed base at his disposal in that other State which he uses for the purpose of performing his work, and the income pertains to that fixed base; or
- (b) income is paid from sources in that other State.
(2) The term "professional services" shall include especially artistic, scientific, athletic, literary, educational or teaching activity independent of any employment, as well as the independent activity of physicians, lawyers, engineers, architects, dentists, auditors, and accountants