Dignen, Bob
York Associates, 1999
Buku Teks SO
Booher, Diana
Prentice-Hall, 1991
Buku Teks SO
Rae, Leslie
McGraw-Hill, 1994
Buku Referensi
Mackenizie, John
Illinois: Dow Jones-Irwin, 1989
Buku Teks SO
oleh Statistical Division United Nations; penerjemah, Agus Riyanto
Citra Grafika Pratama, 2005
Buku Teks