Anna Pankowska Maciej Wygralak Intuitionistic fuzzy sets - an alternative look. 135-140 2003 EUSFLAT Conf. http://www.eusflat.org/publications/proceedings/EUSFLAT_2003/papers/01Pankowska.pdf conf/eusflat/2003 db/conf/eusflat/eusflat2003.html#PankowskaW03