(2015). one step ahead: Towards environmental sustainability. united nation.
Chicago Style (17th ed.) ZitazioaOne Step Ahead: Towards Environmental Sustainability. cairo: united nation, 2015.
MLA (9th ed.) ZitazioaOne Step Ahead: Towards Environmental Sustainability. united nation, 2015.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.