Corinna Cortes Patrick Haffner Mehryar Mohri Positive Definite Rational Kernels. 41-56 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=2777&spage=41 2003 conf/colt/2003 COLT db/conf/colt/colt2003.html#CortesHM03