t-Norm-based addition of fuzzy intervals

T-sum of bell-shaped fuzzy intervals

Fuzzy Sets and Systems

T-sum of sigmoid-shaped fuzzy intervals

Information Sciences: an International Journal

A convexity problem and a new proof for linearity preserving additions of fuzzy intervals

Fuzzy Sets and Systems

Extended triangular norms

Information Sciences: an International Journal

Addition of sigmoid-shaped fuzzy intervals using the Dombi operator and infinite sum theorems

Fuzzy Sets and Systems

Real vector space of LR-fuzzy intervals with respect to the shape-preserving t-norm-based addition

Fuzzy Sets and Systems