Ferris, Kenneth R.
Richard D. Irwin, 1989
Buku Teks
Ferris, Kenneth R.
McGraw-Hill/Irwin, 1996
Buku Teks SO
Gibson, Charles H.
South Western College , 2001
Buku Teks SO
Ferris, Kenneth R.
Richard D. Irwin, 1990
Buku Teks
Black, Geoff
London : Prentice Hall, 2001,
Buku Referensi