*http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WXX-4MTJGVV-4-1&_cdi=7170&_user=10&_orig=browse&_coverDate=01/31/2007&_sk=999039998&view=c&wchp=dGLbVzW-zSkWb&_valck=1&md5=f9d5981e352a9086b0b67c51e3e25369&ie=/sdarticle.pdf | *http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6WXX-4MTJGVV-4-1&_cdi=7170&_user=10&_orig=browse&_coverDate=01/31/2007&_sk=999039998&view=c&wchp=dGLbVzW-zSkWb&_valck=1&md5=f9d5981e352a9086b0b67c51e3e25369&ie=/sdarticle.pdf |