Redirect Notice
 The previous page is sending you to https://www.sciencedirect.com/science/article/pii/S0232439385800354/pdf?md5=882d6938d8b24f09e104083116195444&pid=1-s2.0-S0232439385800354-main.pdf&_valck=1.

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