Hoover Institution Archives:
Online Archives of California has access to 128 manuscript boxes (51.2 linear feet) of Professor Alexander's materials from 1967-2011.
http://www.oac.cdlib.org/findaid/ark:/13030/kt4v19r92k/entire_text/
Proquest Archives:
A collection of 1,500 documents including reports, policy recommendations, and conference information from the last 30 years.