Footnote 4. The Red Mud Project: http://www.redmud.org/home.html

Table 19.4. Data obtained from Cornell Cooperative Extension, Richard, T., http://compost.css.cornell.edu/Factsheets/FS2.html

Problem 9. United Nations Environment Program (UNEP) website, http://www.grida.no/graphicslib/ and the Environment Section of the Eurostat yearbook http://ec.europa.eu/eurostat