APA (7th ed.) Citation

Keene. (1966). The mystery of the 99 steps. Grosset & Dunlap.

Chicago Style (17th ed.) Citation

Keene. The Mystery of the 99 Steps. New York: Grosset & Dunlap, 1966.

MLA (8th ed.) Citation

Keene. The Mystery of the 99 Steps. Grosset & Dunlap, 1966.

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