Erik Assadourian, project director
Island Press, 2012
eBooks
Linda Starke, editor
W.W. Norton & Co.,, 2009
Buku Teks
Vincent, Andrew
Basil Blackwell, 1987
Buku Teks
Laski, Harold J., author
George Allen and Unwin, 1935
Buku Teks
Earthscan Publications , 1999
Buku Teks