Hamilton, Mark, author
Neo-tech books, 2000
Buku Teks
Sorenson, Ritch, author
Prentice-Hall, 2001
Buku Referensi
VNU Business Publications, 1989
Buku Referensi
VNU Business Publications, 1989
Buku Referensi
Nasution, S., author
Jemmans, 1976
Buku Teks