World Bank, 1997
Buku Teks
Anja Seibert-Fohr
Springer, 2012
eBooks
Van Arkadie, Brian, author
Asia Pacific Press at the National Library of Australia, 2004
Buku Teks
McCormick, John, 1954-, author
Wadsworth, 2010
Buku Teks
edited by B.F.G. Johnson
John Wiley & Sons, 1980
Buku Teks