1. S. Abdullah, M. Naeem, and B. Davvaz, Characterizations of regular semigroups by interval-valued fuzzy ideals with thresholds $(\overline{\alpha}, \overline{\beta})$, Annals of Fuzzy Mathematics and Informatics, 8.3 (2014), 419–445.
2. J. Aranzazu, S. Antonio, P. Daniel, F. Javier, and B. Humberto, interval-valued fuzzy sets for color image super-resolution, Advances in Artificial Intelligence, CAEPIA (Nov. 2011), 373–382.
3. R. Biswas, Rosenfeld's fuzzy subgroups with interval-valued membership functions, Fuzzy Sets and Systems, 63.1 (1994), 87–90.
4. H. Bustince, Indicator of inclusion grade for interval-valued fuzzy sets. Application to approximate reasoning based on interval-valued fuzzy sets, International Journal of Approximate Reasoning, 23 (1998), 137–209.
5. Y. Feng, D. Tu, and H. Li, Interval-valued fuzzy hypergraph and interval-valued fuzzy hyperopertions, Italian Journal of Pure and Applied Mathematics, 36 (2016), 1–12.