Niles, Olive S., author
Georgia Scott 1984
Buku Teks
Niles Christensen [and others]
Illinois Scott, Foresman , 1984
Buku Teks
Drucker, Peter F. (Peter Ferdinand), 1909-2005, author
Harper & Brothers, 1959
Buku Teks
Raja Nazrin Shah, author
RNS Publications Sdn Bhd, 2006
Buku Referensi
Chin, Kon Yit, author
Jugra Publications, 2003
Buku Referensi