Treaties and other international acts series. 4537. Uranium reconnaissance, agreement between United States and Brazil. amending agreement of Dec. 26, 1957, effected by exchange of notes signed Washington Dec. 2, 1958; [entered into fores Dec. 23, 1959] and extension agreement effected by exchange of notes signed Washington Dec. 23, 1959, and Jan. 6 and July 6, 1960; [entered into force July 6, 1960].