The official history page:
http://www.kumoricon.org/?page_id=125can be cited as a source, which was a big reason I created it. Also, there is information in the past con books, which are posted as PDFs, which can be cited.
The 2006 and 2007 web sites in their entirety are archived online. I
might be able to get the 2005 site online, as I have some of the data files for it, but I'm not sure if I have the data in its entirety. Meanwhile,
www.archive.org has some of its pages.
I'm seeing if I can get official lists of past guests, exhibitors, and sponsors up on the history page (may not happen immediately, although some of it is in the con books).