Postel, S. (2005). Liquid assets: The critical need to safeguard freshwater ecosystems. Washington, D.C: Worldwatch Institute.
Dyfyniad Arddull ChicagoPostel, Sandra. Liquid Assets: The Critical Need to Safeguard Freshwater Ecosystems. Washington, D.C: Worldwatch Institute, 2005.
Dyfyniad MLAPostel, Sandra. Liquid Assets: The Critical Need to Safeguard Freshwater Ecosystems. Washington, D.C: Worldwatch Institute, 2005.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.