Geraldine E. Rosario Elke A. Rundensteiner David C. Brown Matthew O. Ward Shiping Huang Mapping nominal values to numbers for effective visualization. 80-95 2004 3 Information Visualization 2 http://dx.doi.org/10.1057/palgrave.ivs.9500072 db/journals/ivs/ivs3.html#RosarioRBWH04