APA (7th ed.) Citation

Plotino. (1952). The six enneads. Encyclopaedia Britannica.

Chicago Style (17th ed.) Citation

Plotino. The Six Enneads. Chicago: Encyclopaedia Britannica, 1952.

MLA (9th ed.) Citation

Plotino. The Six Enneads. Encyclopaedia Britannica, 1952.