1. Aceti Associates of Arlington, MA, (2002). Recycling: Why People Participate; Why They Don’t, A Barrier/Motivation Inventory: The Basis of Community-Based Social Marketing. Retrieved April 1,2010, from http://www.acetiassociates.com/pubs/curbside.pdf.
2. Belum terlewat jayakan kempen kitar semula (2003, Oktober 29). Harian Metro, p. 10.
3. The Influence of an Educational Computer Game on Children's Cultural Identities;Chen;Educational Technology & Society,2010
4. Encyclopedia of Atmospheric Environment (2000). Retrieved April 20,2010 http://www.ace.mmu.ac.uk/eae/sustainability/Older/Waste_Recycling.html.
5. Kitar Semula (2007), Kitar Semula .Retrieved April 8, 2008 from http://www.kitarsemula.com.