National University of Singapore, [date of publication not identified]
Buku Referensi
National University of Singapore, [date of publication not identified]
Buku Referensi
Gibaldi, Joseph
The Modern Language Association, 2003
Buku Teks
Johson, Jean
Bedford Books, 1987
Buku Teks
Fisher, Andrew, 1941-
Population Council, 2002
Buku Teks