Redirect Notice
 The previous page is sending you to https://www.sciencedirect.com/science/article/pii/S0007153687801845/pdf?md5=cc9deff12be4f3aac1ec1564c7c5348f&pid=1-s2.0-S0007153687801845-main.pdf&_valck=1.

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