Redirect Notice
 The previous page is sending you to https://www.sciencedirect.com/science/article/pii/S0168797299800139/pdf?md5=c20e4344e49871701668e616f18bb548&pid=1-s2.0-S0168797299800139-main.pdf.

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