http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VBW-47N61RY-7&_user=10&_coverDate=07%2F31%2F1988&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1232323172&_rerunOrigin=scholar.google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=2d78bad7df716be0d4906369854464b1

谢谢。