Subject to Article 22 (Directors' Fees), income derived by an individual who is a resident of a Contracting State in respect of professional services or other independent personal services shall be taxable only in that State. However, in the following circumstances such income as is derived from services performed in the other Contracting State may be taxed in the other Contracting State:
a) if the individual's stay in the other State is for a period or periods aggregating 183 days or more in the taxable year; or
b) if the individual has a fixed base regularly available to him in the other Contracting State for the purpose of performing his activities; in that case, only so much of the income as is attributable to that fixed base may be taxed in that other State.
