Ralph Waldo Emerson, Alfred R. Ferguson (1965). “Journals and Miscellaneous Notebooks of Ralph Waldo Emerson, Volume V: 1835-1838”, p.335, Harvard University Press
Aeschylus (1956). “Aeschylus: The suppliant maidens, The Persians, translated by S. G. Benardete. Seven against Thebes, Prometheus bound, translated by D. Grene”