Allaby, Michael
Oxford University Press, 1992
Buku Referensi
Neushul, Michael
Hamilton, 1974
Buku Teks SO
Neushul, Michael
Hamilton, 1974
Buku Teks SO
Wilson, Carl L.
Holt, Rinehart and Winston, 1962
Buku Teks SO
Dawes, Clinton J.
"New York: John Wiley & Sons, 1981",
Buku Teks