In their seminal report, "Economic Accounting for Sustainable Development", Yusuf Ahmad, Salah El Serafy and Ernst Lutz compiled papers from several UNEP-World Bank sponsored workshops, convened after 1983, on how to develop environmental accounting as a public policy tool. The central theme of all of the authors' arguments is that the system of national accounts (SNA), as it traditionally calculates income, omits important aspects of economic development that ought to be included. One important disagreement on environmentally adjusted indicators is presented by Anne Harrison and Salah El Serafy in their respective chapters. Harrison argues that appropriate adjustments ought to be made within the existing SNA framework, while El Serafy suggests a redefinition of what constitutes intermediate and final demand. In his view, the SNA should not consider the sale of natural capital as generating value added, while at least part of the income generated from this sale should be excluded from GDP and net product. This would effectively allow GDP to continue to be used extensively.