37 The valuation of environmental costs and benefits is constantly evolving, with new research continually being funded by the UK government and its agencies. Research covers both methodological development and the estimation of values. There are a number of valuable reference sources that discuss valuation issues in depth.20 The following paragraphs provide information on government research and guidance on the quantification and monetisation of impacts, including which departments are sponsoring research. As this is a developing field, policy makers are encouraged to refer to the Green Book homepage, in order to locate the most up to date information.
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20 See, for example, "Economic Valuation with Stated Preference Techniques: Summary Guide", available on the DfT website at http://www.dft.gov.uk.