APA (7th ed.) Citation

Sands, B., & Walpole, H. A key to the impenetrable secret.

Chicago Style (17th ed.) Citation

Sands, Benjamin, and Horace Walpole. A Key to the Impenetrable Secret.

MLA (9th ed.) Citation

Sands, Benjamin, and Horace Walpole. A Key to the Impenetrable Secret.

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