APA (7th ed.) Citation

Henry, O. (1974). The unknown quantity and other stories / (by O. Henry). Hodder and Stoughton.

Chicago Style (17th ed.) Citation

Henry, O. The Unknown Quantity and Other Stories / (by O. Henry). London: Hodder and Stoughton, 1974.

MLA (9th ed.) Citation

Henry, O. The Unknown Quantity and Other Stories / (by O. Henry). Hodder and Stoughton, 1974.

Warning: These citations may not always be 100% accurate.