Dyfyniad APA

(1991). Costing the earth. London: The economist books.

Dyfyniad Arddull Chicago

Costing the Earth. London: The economist books, 1991.

Dyfyniad MLA

Costing the Earth. London: The economist books, 1991.

Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.