Dyfyniad APA

hartwick, J. M. (1989). Non-Renewable resources extraction programs and markets. Harwood academic Pub.

Dyfyniad Arddull Chicago

hartwick, John M. Non-Renewable Resources Extraction Programs and Markets. Chur: Harwood academic Pub, 1989.

Dyfyniad MLA

hartwick, John M. Non-Renewable Resources Extraction Programs and Markets. Harwood academic Pub, 1989.

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