Macmillan Press, 1990
Buku Teks
Santayana, George, author
Collier Books, 1961
Buku Teks
Regev, Motti, author
UK Polity, 2013
Buku Teks
Beaver, Frank E., author
Twayne Publishers, 1994
Buku Referensi
Murray, Darrel L., author
Addison-Wesley, 1971
Buku Teks