Eulalia Szmidt Janusz Kacprzyk Classification with Nominal Data Using Intuitionistic Fuzzy Sets. 76-85 2007 conf/ifsa/2007 IFSA (1) http://dx.doi.org/10.1007/978-3-540-72950-1_8 db/conf/ifsa/ifsa2007.html#SzmidtK07