CIA (2009) Singapore. CIA (Content Source);Peter Saundry (Topic Editor) . “Singapore”. In: Encyclopedia of Earth. Eds. Cutler J. Cleveland (Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment). First published in the Encyclopedia of Earth October 13, 2009; Last revised Date October 13, 2009; Retrieved October 22, 2010
EEA.(1999). Towards Environmental Pressure Indicators for the EU, 1st edn. European Environment Agency.
EIA (2007) Energy profile of Singapore. In: Cutler JC, Langdon DC (eds) Encyclopedia of Earth. Energy Information Administration (Content source) Washington, D.C.: Environmental Information Coalition, National Council for Science and the Environment.
Johnson, D. 2008. Environmental indicators: their utility in meeting the OSPAR Convention’s regulatory needs. – ICES Journal of Marine Science, 65: 1387–1391.
OECD. 1993. OECD Core set of indicators for environmental performance reviews: a synthesis report by the Group on the State of the Environment. OECD, Environment Monographs, 83: OECD/GD(93)179.