Meriam-Webster, Incoporate, 1995
Buku Referensi
Corstius, Jan Brandt, author
Random House, 1968
Buku Teks
by Rewey Belle Inglis ... [et al.]
Harcourt, Brace, 1945
Buku Teks
edited by Joseph T. Shipley
Philosophical Library, 1946
Buku Referensi
edited by Joseph T. Shipley
Philosophical Library, 1946
Buku Referensi