Redirect Notice
 The previous page is sending you to https://www.sciencedirect.com/science/article/pii/S0007153680800854/pdf?md5=6c54d0c752b0120b5f53914d554178f1&pid=1-s2.0-S0007153680800854-main.pdf.

 If you do not want to visit that page, you can return to the previous page.