(1991). Costing the earth. London: The economist books.
Dyfyniad Arddull ChicagoCosting the Earth. London: The economist books, 1991.
Dyfyniad MLACosting the Earth. London: The economist books, 1991.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.