Nicolò Cesa-Bianchi Alex Conconi Claudio Gentile Regret Bounds for Hierarchical Classification with Linear-Threshold Functions. 93-108 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3120&spage=93 2004 conf/colt/2004 COLT db/conf/colt/colt2004.html#Cesa-BianchiCG04