Income derived by a resident of a Contracting State in respect
of professional services or other 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 the income as is attributable to that fixed base. For this
purpose, where a resident of a Contracting State is present in the
other Contracting State for a period or periods exceeding in the
aggregate 183 days in any twelve-month period commencing or ending
in any fiscal year, he shall be deemed for that fiscal year to have
a fixed base regularly available to him in that other State and the
income that is derived from his activities referred to above that
are performed in that other State shall be attributable to that
deemed fixed base.
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.
