Edgell, David L. (David Lee), Sr., 1938
Routledge, 2016
Buku Teks
Richard Creath, editor
Springer, 2012
eBooks
Lewis, David E., author
Springer, 2012
eBooks
Austria : The Opec fund dor International Development (OFID), 2006,
Majalah, Jurnal, Buletin
Artikel Jurnal