Stewart, Rosemary
McGraw-Hill, 1976
Buku Teks
Gaster, Lucy, 1940-
Open University Press, 1995
Buku Teks
Knoll, Robert E.
Harcourt, Brace and Company, 1959
Buku Teks SO
Coulmas, Florian
Cambridge University Press, 2005
Buku Teks SO
Australian Agency for International Development, 1998
Buku Teks