Duggan, Francis X
Twayne, 1966
Buku Teks
Hankes, Elmer Joseph
The Hankes Foundation, 1992
Buku Teks
Laski, Harold J., author
George Allen and Unwin, 1948
Buku Teks
Laski, Harold J., author
George Allen and Unwin, 1950
Buku Teks
Laski, Harold J., author
George Allen and Unwin, 1955
Buku Teks