Dyfyniad APA

(2011). Keeping track of our changing environment from Rio to Rio + 20 (1992-2012). United Nations Environment Programme.

Dyfyniad Arddull Chicago

Keeping Track of Our Changing Environment from Rio to Rio + 20 (1992-2012). Nairobi, Kenya: United Nations Environment Programme, 2011.

Dyfyniad MLA

Keeping Track of Our Changing Environment from Rio to Rio + 20 (1992-2012). United Nations Environment Programme, 2011.

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