United States. Department of the Treasury. "U.S. and Spain to discuss tax treaty, March 30, 1966, Release Number f-421," in United States. Department of the Treasury. "Volume 153," Press Releases of the United States Department of the Treasury (February 1, 1966 - March 30, 1966) : 755-756. https://fraser.stlouisfed.org/title/6111/item/586996/toc/540000 , accessed on June 24, 2024.