(a) Subject at all times to special call or direction by the two Governments, meetings of the Commission shall be held at such times and places in the United States and Canada as the Commission or the Chairman may determine and in any event shall be held each year at Washington in April and at Ottawa in October, beginning ordinarily on the first Tuesday of the said months.(b) If the Commission determines that a meeting shall be open to the public, it shall give such advance notice to this effect as it considers appropriate in the circumstances.