http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VBN-4WBC1WW-1-K&_cdi=5931&_user=119223&_pii=S0301751609001161&_origin=&_coverDate=09%2F01%2F2009&_sk=999069998&view=c&wchp=dGLbVzW-zSkWz&md5=190e6103e5542fe277633f4aa9263159&ie=/sdarticle.pdf