Crawford, F. Robert
Prentice-Hall, 1973
Buku Teks
Gregory, Robert Henry
Chatto and Windus, 1963
Buku Teks
Gleim, George A.
McGraw-Hill, 1956
Buku Teks
Petrou, Maria
John Wiley & Sons Ltd, 2010
Buku Teks
Couger, J. Daniel
John Wiley & Sons, 1984
Buku Teks