Couso, I., Garrido, L., & Sánchez, L. (2014). The notion of roughness of a fuzzy set. Fuzzy Sets and Systems, 249, 114-127. https://doi.org/10.1016/j.fss.2014.02.013
Couso, I., & Sánchez, L. (2017). Additive similarity and dissimilarity measures. Fuzzy Sets and Systems, 322, 35-53. https://doi.org/10.1016/j.fss.2016.12.013