Kolb, John H.
Houghton Mifflin , 1952
Buku Teks
The United States Departement of Agriculture, 1976
Buku Teks
Iowa State University Press , 1964
Buku Teks
Brunner, Edmund de S., author
McGraw-Hill, 1933
Buku Teks
White, Edwin Harold
Prentice-Hall, 1980
Buku Teks