O`Sullivan, Terence, author
Macmillan, 1999
Buku Teks
Hancock, Betsy Ledbetter, author
Prentice-Hall, 1982
Buku Teks
Skidmore, Rex A. (Rex Austin), author
Prentice Hall International, 1991
Buku Teks
Ferguson, Elizabeth A., author
J.B. Lippincott, 1975
Buku Teks
Geeorge Allen , 1971
Buku Teks