There was a Fuzzy Logic package for Mathematica 5, is it available for 9 or is there something similar? Or a book with electronic supplement?
The page for this add-on can be found here:
http://www.wolfram.com/products/applications/fuzzylogic/
It has not been updated to work on versions past version 5 of Mathematica by its creators. I’ve seen some people working with fuzzy logic in Mathematica, but they generally write their own package for their research.