Wheeler, James O., author
John Wiley & Sons, 1986
Buku Teks
Alexander, John W., author
Prentice-Hall, 1979
Buku Teks
Hartshorn, Truman Asa, author
Prentice-Hall, 1988
Buku Teks
Thatcher, W.S., author
English University Press, 1957
Buku Teks
Knox, Paul, author
Edward Arnold , 1994
Buku Teks