Auerbach, Robert D., author
Macmillan, 1989
Buku Teks
Black, Tyrone
Business Publications, Inc., 1981
Buku Teks
Miller, Roger LeRoy, author
McGrow-Hill, 1985
Buku Teks
Pritchard, Leleand J.
Hougton Mifflin Company, 1958
Buku Teks
Burstein, N. L.
Massachusetts Schenkman Publication , 1963
Buku Teks