Wold Bank, 2004
Buku Teks
Dezan Shira, editor, Chris Devonshire-Ellis, editors
[Springer, ], 2012
eBooks
Price Waterhouse, 1966
Buku Teks
edited by Marianne Chalmers and Martine Pierquin
Oxford University Press, 2002
Buku Referensi
Mueller, Rudolf, author
Fritz Knapp Verlag, 1972
Buku Teks