When is there a representer theorem? Vector versus matrix regularizers

Andreas Argyriou Charles A. Micchelli Massimiliano Pontil When is there a representer theorem? Vector versus matrix regularizers http://arxiv.org/abs/0809.1590 2008 CoRR abs/0809.1590 db/journals/corr/corr0809.html#abs-0809-1590 informal publication