APA aipamena

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

Chicago Style aipamena

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

MLA aipamena

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

Kontuz: berrikusi erreferentzia hauek erabili aurretik.