Loomis, Mary E.S.
Prentice-Hall, 1983
Buku Teks SO
Stallings, William
Prentice-Hall, 1994
Buku Teks SO
Marston, R.M.
Newnes, 1993
Buku Teks
Indonesia. Biro Pusat Statistik
Biro Pusat Statistik, 1963
Buku Referensi
Brindley, Keith
A Butterworth-Heinemann Book, 1994
Buku Teks