Erskine, Robert
Elex Media Komputindo, 1987
Buku Teks SO
Jones, Douglas Samuel
Oxford University Press, 1988
Buku Teks
Rollins, Dan
Macmillan, 1985
Buku Teks
Goody, Roy W.
New York Glencoe 1992,
Buku Referensi
Leventhal, Lance A.
Prentice-Hall, 1987
Buku Teks