Yuji Yoshida Masami Yasuda Jun-ichi Nakagami Masami Kurano A new evaluation of mean value for fuzzy numbers and its application to American put option under uncertainty. 2614-2626 2006 157 Fuzzy Sets and Systems 19 http://dx.doi.org/10.1016/j.fss.2003.11.022 db/journals/fss/fss157.html#YoshidaYNK06