URLDate
Verified		Extra Software
Requirements
(if any)		Access
Conditions		Notes
http://dx.doi.org/10.1016/0038-0717(79)90048-8DOI Link
http://www.sciencedirect.com/science/article/pii/0[...]10/08/2015 Item is within a limited-access website
http://ac.els-cdn.com/0038071779900488/1-s2.0-0038[...]10/08/2015 PDF Reader Item is within a limited-access website