1. 2. United Nations Earth Summit . Agenda 21. The United Nations Programme for Actions From Rio, U.N., USA.
2. 3. European Commission (COM 1992) . Towards Sustainability: A European Community Programme of Policy and Action in Relation to the Environment and Sustainable Development COM(92)23 . Final Volume II European Commission, Brussels.
3. 4. European Commission . Communication from the Commission (COM(97(9)). Environmental taxes and charges in the Single Market. 1997 .
4. 5. J. Buckland, and T. Zabel Economic instruments of water management and financing of infrastructure. InSelected Issues in Water Resources Management in Europe.Balkema, Rotterdam. 1998 .