Daniel, Wayne W.
Houghton Miffiln, 1989
Buku Teks SO
Levin, Richard I.
Prentice-Hall, 1998
Buku Teks SO
Manly, Bryan F.J.
CRC Press, Taylor & Francis Group, 2009
Buku Teks SO
Chao, Lincoln L.
Prentice-Hall, 1981
Buku Teks SO
Mendenhall, William
Duxbury Press, 1971
Buku Teks SO