APA (7th ed.) Citation

Gibbon, E. (1952). The Decline and fall of the Roman empire. Encyclopaedia Britannica.

Chicago Style (17th ed.) Citation

Gibbon, Edward. The Decline and Fall of the Roman Empire. Chicago [etc.]: Encyclopaedia Britannica, 1952.

MLA (9th ed.) Citation

Gibbon, Edward. The Decline and Fall of the Roman Empire. Encyclopaedia Britannica, 1952.