Hongying Zhang Wenxiu Zhang Changlin Mei Entropy of interval-valued fuzzy sets based on distance and its relationship with similarity measure. 449-454 2009 22 Knowl.-Based Syst. 6 http://dx.doi.org/10.1016/j.knosys.2009.06.007 db/journals/kbs/kbs22.html#ZhangZM09