(Earth Works Group (U.S. (1989). 50 simple things you can do to save the earth. Earthworks Press.
Dyfyniad Arddull Chicago(Earth Works Group (U.S. 50 Simple Things You Can Do to Save the Earth. .Berkeley, CA: Earthworks Press, 1989.
Dyfyniad MLA(Earth Works Group (U.S. 50 Simple Things You Can Do to Save the Earth. Earthworks Press, 1989.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.