Pope, Rob, author
Routledge, 2005
Buku Teks
Lowie, Robert H., author
Holt Rinehart and Winston, 1937
Buku Teks
Heller, Agnes
Routledge & Kegan Paul, 1982
Buku Teks
Sabine, George H., author
Henry Holt, 1950
Buku Teks
Sabine, George H., author
Henry Holt , 1955, 1956
Buku Teks