Clark, Tom S.
Cambridge University Press, 2019
eBooks
Spaeth, Harold J.
W.H.Freeman and Company, 1976
Buku Teks
Rehnquist, William H.
William morrow and company,inc., 1987
Buku Teks
Johnson, Gerald W.
William Morrow and Company, 1962
Buku Teks
edited by Burke Marshall
United States International Communication Agency, 1982
Buku Teks