KNight, Bruce Winton
Alfred A. Knoff , 1952
Buku Teks
Hoag, Erleen J.
Prentice-Hall, 1991
Buku Teks
McKenna, John R.
Harper and Row , 1971
Buku Teks
Keiser, Norman F., author
John Wiley & Sons, 1960
Buku Teks
Boulding, Kenneth E. (Kenneth Ewart), 1910-1993, author
Harper & Row, 1966
Buku Teks