Gertrude Stein (2016). “THE AUTOBIOGRAPHY OF ALICE B. TOKLAS (Modern Classics Series): Glance at the Parisian early 20th century avant-garde (One of the greatest nonfiction books of the 20th century)”, p.70, e-artnow
Quoted by Thornton Wilder in December 14-15, 1956, interview with Richard Goldstone. "Writers at Work: The Paris Review Interviews, First Series", 1958.
Reported in Donald Sutherland, Gertrude Stein: A Biography of Her Work (1951). Stein's companion Alice B. Toklas, who was with her at her death, reported Stein's words as, "What is the answer? ... In that case... what is the question?" (Alice B. Toklas, What Is Remembered [1963]), and did not identify these specifically as the last words.