Krzysztof Dyczkowski Maciej Wygralak On triangular norm-based generalized cardinals and singular fuzzy sets. 211-226 2003 133 Fuzzy Sets and Systems 2 http://www.sciencedirect.com/science/article/B6V05-472JVMX-X/2/a4f2a4dbdafff09d4dfe52d60a14cab9 db/journals/fss/fss133.html#DyczkowskiW03