Steinfeld, Jake, author
American Management Association, 2006
eBooks
Stern, Michael
Random House, 1953
Buku Teks
Friedrich, Carl J., author
Boston University Press, 1967
Buku Teks
Schuman, Frederick L., author
Alfred A. Knopf, 1949
Buku Teks
Seoul International Publicity Corp 1974,
Buku Teks