(2015). one step ahead: Towards environmental sustainability. united nation.
Chicago-referens (17:e uppl.)One Step Ahead: Towards Environmental Sustainability. cairo: united nation, 2015.
MLA-referens (9:e uppl.)One Step Ahead: Towards Environmental Sustainability. united nation, 2015.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.