3Zadeh L A. What's soft computing[J]. Soft Computing, 1997, 1(1):Preface.
4Shyllon E A, Olaleye J B, Olunloyo V O S. Litho-seismic data handling for hydrocarbon reservoir estimate., fuzzy system modeling approach[J]. Journal of Petroleum Science and Engineering, 2001, 31:165--173.
5Ludwig B. On the sustainability of future energy systems[J]. Energy Conver Mgmt, 1997, 3541765--1776.
6Phillis Y A, Andriantiatsahoiliniaina L A. Sustainability: an Ill-defined concept and its assessment using fuzzy logic[J]. Ecological Economics, 2001, 37:435--456.
7Van Leekwijck W, Kerre E E. Defuzzification:criteria and classification [J]. Fuzzy Sets and Systems, 1999, 108:159--178.
