The Proceedings of the National Academy of Sciences (U.S.) recently had a special issue on "Spatial Demography"

 

The issue of PNAS is Volume 102, Issue 43 and is available online at:

 

http://www.pnas.org/content/vol102/issue43/

 

With a PSU account you should be able to access all the PDFs from campus.  If you need to access them from home, you will need to go through a Penn State portal.