Jason Weston Ronan Collobert Fabian H. Sinz Léon Bottou Vladimir Vapnik Inference with the Universum. 1009-1016 2006 conf/icml/2006 ICML http://doi.acm.org/10.1145/1143844.1143971 db/conf/icml/icml2006.html#WestonCSBV06