This primary source comes from the Collection DDE-EPRES: Eisenhower, Dwight D.: Papers as President of the United States.
Full Citation: Press Clipping - United States Note to Soviet Union on Spy Flights; 5/12/1960; U-2 Incident - Press (1); Subject Files, 1953 - 1961; Collection DDE-EPRES: Eisenhower, Dwight D.: Papers as President of the United States; Dwight D. Eisenhower Library, Abilene, KS. [Online Version, https://docsteach.org/documents/document/us-spy-flights, May 9, 2024]