Which literary work is not by Ernest Hemingway?

Ernest Hemingway (1899 - 1961) : is an American Novelist.

Major Works:
- For whom the Bell Tolls,
- The Old Man and the Sea,
- A Farewell to Arms,
- The Sun Also Rises,
- Death in the Afternoon,
- To Have and Have Not.

Heart of Darkness is a novel by Joseph Conrad.

Source: Britannica