Tetsuji Kuboyama Kouichi Hirata Kiyoko F. Aoki-Kinoshita An Efficient Unordered Tree Kernel and Its Application to Glycan Classification. 184-195 2008 PAKDD http://dx.doi.org/10.1007/978-3-540-68125-0_18 conf/pakdd/2008 db/conf/pakdd/pakdd2008.html#KuboyamaHA08