Heady, Earl O., author
Prentice-Hall, 1952
Buku Teks
Barlowe, Raleigh, author
Prentice-Hall, 1961
Buku Teks
Artikel Jurnal
Ross, Robert C., author
McGraw-Hill, 1951
Buku Teks
the Australian Agricultural Economic Society, 1989
Majalah, Jurnal, Buletin