Scott, Foresman and Company, 1984
Buku Teks
Harmon, Sharon Koomen, author
John Wiley & Sons, 2011
Buku Teks
Traister, John E., author
Reston Publishing Company, 1979
Buku Referensi
Sykes, Peter
Longmans, 1966
Buku Referensi
Orient Mercur-Verlag, 1958
Buku Teks