Dyere, Everett D., author
McGraw-Hill, 1979
Buku Teks
National Council of Farmer Cooperatives , 1992
Buku Teks
Makkai, Adam
Barrons, 1995
Buku Teks
Patrick, John
Macmillan Publishing Company, 1984
Buku Teks
Quint, Howard H
Dorsey Press, 1968
Buku Teks