Keep, John
Frederick A. Praeger, 1964
Buku Teks
Frederick A, Praeger; George Allen and Unwin Ltd., 1964
Buku Teks
Gallagher, Matthew P., author
Frederick A. Preager, 1963
Buku Teks
Carr, Edward Hallet, author
Macmillan, 1954
Buku Teks
Stephan, John J.
Stanford University Press, 1994
Buku Teks