Lucretius ; [translated by Rolfe Humphries] . The discourses of Epictetus / [translated by George Long] . The meditations of Marcus Aurelius / [translated by George Long] . The six Enneads / Plotinus ; [translated by Stephen MacKenna and B.S. Page]. -- 2nd ed. -- Encyclopædia Britannica, c1990. -- (Great books of the Western World / Mortimer J. Adler, editor in chief ; 11).