Treaties and other international acts series. 3131. Mutual defense assistance in Indochina, agreement between United States and Cambodia, France, Laos, and Viet-Nam, amending annex to agreement of Dec. 23, 1950, effected by exchange of notes between United States and France, dated Saigon Aug. 10 and Sept. 8, 1951, between United States and Viet-Nam dated Saigon Aug. 10 and Sept. 17, 1951, between United States and Laos dated Saigon Aug. 16, 1951 and at Vientiane Nov. 6, 1951. between United States and Cambodia dated Saigon Aug. 16, 1951 and at Phnom-Penh Jan. 7, 1952; entered into force Jan. 7, 1952, operative retroactively July 1, 1951.