http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WHV-4H9YC71-1-1P&_cdi=6860&_user=119223&_pii=S0147596705000673&_origin=&_coverDate=12%2F31%2F2005&_sk=999669995&view=c&wchp=dGLbVlz-zSkzS&md5=53c427308135783547323965fed9e12c&ie=/sdarticle.pdf