Income derived by a resident of a Contracting State in respect
of professional services or other independent activities of a
similar character shall not be taxable in the other Contracting
State if he is subject to tax in respect thereof in the Contracting
State of which he is a resident 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 Contracting State but only so
much of it as is attributable to that 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
