Check this link
h**p://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TWR-3YMWM7Y-46&_coverDate=04%2F30%2F1995&_alid=512962869&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=5569&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=0d214c13dbd9c55efb8bc77786f14025