“…In the equations, ε is a stop threshold, m is a fuzziness exponent, and || * || is a norm expressing the similarity between any measured datum and the centroid. Regarding both ratings and additional items' information, several works have employed the fuzzy c-means clustering [11,38,40,66,73,87,101,103,128,129,131,141,142], and also similar approaches such as relational fuzzy subtractive clustering [121], co-clustering [45,49,114,133], picture fuzzy clustering [123], folksonomy-focused intuitionistic fuzzy agglomerative hierarchical clustering [43], fuzzy geographical clustering [119], linear fuzzy clustering [48], and other fuzzy clustering approaches [18,29,35,39,61,64,143].…”