Under Article XIV of the convention, an alien who is a resident of Denmark but who is temporarily present within the United States for the purpose of teaching, lecturing, or instructing at any university, college, school, or other educational institution, situated within the United States, is, for a period not exceeding two years from the date of his arrival in the United States, exempt for taxable years beginning on or after January 1, 1948, from Federal income tax on remuneration received for such services. It shall be deemed that such alien coming to the United States for the purposes indicated has, for a period of not more than two years immediately succeeding the date of his arrival within the United States for such purposes, the tax status of a nonresident alien in the absence of proof of his intention to remain indefinitely in the United States.