Gross, M. Grant
Prentice-Hall, 1995
Buku Teks
Benham, Frederic
New York, N.Y. Pitman 1947,
Buku Teks
Kendrick, M. Slade
Houghton Mifflin , 1951
Buku Teks
Holmes, Parker M.
South-Western Publishing Co., 1960
Buku Teks
Norris, Christopher M.
London A & C Black 1993,
Buku Teks