Bone, Hugh A., author
University of Washington Press, 1958
Buku Teks
Mittleman, Earl N.
New York University, [date of publication not identified]
Buku Teks
Hart, Albert Gailord, 1909-, author
Twentieth Century Fund, 1953
Buku Teks
Downs, Frederick
W.W. Norton & Company, 1991
Buku Teks
Barclay, Glen St. John, 1930-, author
Oxford University Press, 1985
Buku Teks