5Herrera F,Martinez L.A 2-tuples fuzzy linguistic represent model for computing with words[J].IEEE Transactions on Fuzzy Systems,2000,8(6):746-752.
6Herrera F,Martinez L.A Model based on linguistic 2-tuples for dealing with multi-granularity hierarchical linguistic contexts in multiexpert decision-making[J].IEEE Transactions on Systems,Man and Cybernetics-Part B:Cybernetics,2001,31(2):227-234.