Michael May Christine Körner Dirk Hecker Martial Pasquier Urs Hofmann Felix Mende Handling missing values in GPS surveys using survival analysis: a GPS case study of outdoor advertising. 78-84 2009 KDD Workshop on Data Mining and Audience Intelligence for Advertising http://doi.acm.org/10.1145/1592748.1592759 conf/kdd/2009adkdd db/conf/kdd/adkdd2009.html#MayKHPHM09