United States. Department of the Treasury. "U.S. and Costa Rica sign Exchange Agreement, September 6, 1961," in United States. Department of the Treasury. "Volume 127," Press Releases of the United States Department of the Treasury (August 1, 1961 - September 28, 1961) : 230-234. https://fraser.stlouisfed.org/title/6111/item/586970/toc/538556 , accessed on June 24, 2024.