Hichem Sahbi Nozha Boujemaa Validity of Fuzzy Clustering Using Entropy Regularization. 177-182 2005 FUZZ-IEEE https://doi.org/10.1109/FUZZY.2005.1452389 conf/fuzzIEEE/2005 db/conf/fuzzIEEE/fuzzIEEE2005.html#SahbiB05