References

1. "The island of Texel towards a sustainable energy future" (20/12/2014):

http://www.capgemini.com/blog/sustainability-blog/2013/12/the-island-of-texel-towards-a-sustainable-energy-future-0

2. "Hierarchy of Societal Needs" (1/12/2011):

https://gaianomy.wordpress.com/2011/12/04/hierarchy-of-social-needs-by-gaianomy-at-last/

3. "Criteria of Sustainability" (1998):

http://www.holocene.net/sustainability/sustainability.htm