Artikel 21

1. An individual who is a resident of one of the States at the beginning of his visit to the other State and who, at the invitation of the Government of that other State or of a university or other accredited educational institution situated in that other State, visits that other State for the primary purpose of teaching or engaging in research, or both, at a university or other accredited educational institution shall be exempt from tax in that other State on his income from such teaching or research for a period not exceeding two years from the date of his arrival in that other State.
2. The provisions of this Article shall not apply to income from research if such research is undertaken primarily for the private benefit of a specific person or persons.