Barnard, C. J.
Harlow Longman Scientific & Technical , 1993
Buku Teks
Pesic, Peter
MIT Press, 2000
Buku Teks
edited by Robert E. Goodin, Charles Tilly
Oxford University Press, 2008
Buku Referensi
Denscombe, Martyn, author
Open University Press, 2012
Buku Teks
Sommer, Robert, author
Oxford University Press, 2001
Buku Teks