Tooley, Michael H., author
Boston Newnes, 1992
Buku Teks
Loomis, Mary E.S., author
Prentice-Hall, 1983
Buku Teks
Stallings, William, author
Prentice-Hall, 1994
Buku Teks
Indonesia. Biro Pusat Statistik
Biro Pusat Statistik, 1963
Buku Referensi
Brindley, Keith, author
A Butterworth-Heinemann Book, 1994
Buku Teks