Caldwell, Wallace Everett, author
Holt, Rinehart and Winston, 1963
Buku Teks
Sinnigen, William G.
Macmillan, 1981
Buku Teks
Casson, Lionel, author
United States of America: Minerva Press, 1959
Buku Teks
Blois, Lukas de, author
Routledge, 1997
Buku Teks
Armstrong, A.H., author
Newman Press, 1949
Buku Teks