http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6T16-4DCWKCY-3-1&_cdi=4882&_user=119223&_pii=S0167527304005558&_origin=search&_coverDate=07%2F20%2F2005&_sk=998979996&view=c&wchp=dGLbVzW-zSkzV&md5=60d2acaa43d7a58cee1996091256cb1a&ie=/sdarticle.pdf