(3) Notwithstanding the provisions of paragraphs (1) and (2) of this Article, income derived from activities performed in a Contracting State by an artiste or sportsman shall be taxable only in the Contracting State of which the artiste or sportsman is a resident if the visit to the first mentioned Contracting State is wholly or substantially supported by public funds of one or both of the Contracting States or of political subdivisions or local authorities thereof.