Yubin Kuang Kalle Åström Lars Kopp Magnus Oskarsson Martin Byröd Optimizing Visual Vocabularies Using Soft Assignment Entropies. 255-268 2010 ACCV (4) http://dx.doi.org/10.1007/978-3-642-19282-1_21 conf/accv/2010-4 db/conf/accv/accv2010-4.html#KuangAKOB10