edited by Kirsten Malmkjær
Routledge, 2004
Buku Referensi
Wright, Samson
Oxford University Press, 1928
Buku Referensi
Polyanin, Andrei D.
Chapman &Hall/CRC, 2008
Buku Referensi
Chiang, Alpha C., 1927-
Holt, Rinehart and Winston, 1968
Buku Teks
Norman K. Denzin, Yvonna S. Lincoln, editors
Sage Publications, 2000
Buku Referensi