Levinson, Paul, author
Routledge, 1999
Buku Teks
Gladney, Henry M., author
Springer, 2007
Buku Teks
Niblett, G.B.F., author
OECD, 1971
Buku Teks
Calder, Alan, author
kogan page limited, 2005
Buku Teks
Manger, Jason J., author
McGraw-Hill, 1995
Buku Referensi