Churchill, Anthony, author
The Johns Hopkins University , 1972
Buku Teks
Churchill, Anthony, author
John Hopkins University Press, 1972
Buku Teks
Booth, John A., author
Westerview Press, 1993
Buku Teks
Rodriguez, Mario
Prentice-Hall, 1965
Buku Teks
Liss, Sheldon B.
Westview Press, 1991
Buku Teks