Clarke, Geoffrey M
American Elsevier Publishing, 1969
Buku Teks
Michael S. Lewis-Beck, editor
Sage Publications, Topan Publishing, 1993
Buku Referensi
Zolman, James F.
Oxford University Press, 1993
Buku Teks
Wallraven, Douglas W., author
CRC Press, 2012
Buku Teks
Myers, Anne, author
Wadsworth and Cengage Learning, 2012
Buku Teks