Παραπομπή APA

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

Παραπομπή Chicago Style

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

Παραπομπή MLA

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