Skidmore, David, author
Open University Press, 2004
Buku Teks
Ferre, John P., author
Charles E. Merrill Pub. Co., 1983
Buku Referensi
Pollack, Merrill
Bobbs-Merrill, 1962
Buku Teks
Voe, Merrill De
Prentice-Hall, 1957
Buku Teks
Elliot, Mabel A.
arper & Brothers, 1961
Buku Teks