Triangular norms and their hierarchy are investigated. A localisation of cl
assical T-s norms and various other norms is obtained. The class of t-norms
proposed by Zimmermann, Fuzzy Set Theory and its Applications, Kluwer, Dor
drecht, 1991 is placed in the above hierarchy and a proof that it is weaker
(see Butnariu, Fuzzy Sets and Systems 69 (1995) 241-255) then T-1 conclude
s the paper. (C) 2001 Elsevier Science B.V. All rights reserved.