1. Rogner HH, Popescu A. An introduction to energy. In: Goldemberg J (Chair), editor. World energy assessment: energy and the challenge of sustainability. New York: United Nations Development Programme, 2000.
2. The technical and economic feasibility of biomass gasification for power generation;Bridgwater;Fuel,1995
3. Neeft JPA, Knoef HAM, Onaji P. Behaviour of tar in biomass gasification systems. Tar related problems and their solutions. Novem Report No. 9919. Energy from Waste and Biomass (EWAB), The Netherlands, 1999.
4. Multi-stage reactor for thermal gasification of wood;Bui;Energy,1994
5. Milne TA, Evans RJ. Biomass gasification “tars”: their nature, formation and conversion. NREL, Golden, CO, USA, Report no. NREL/TP-570-25357, 1998.