http://www.wsdot.wa.gov/Projects/Viaduct/About
http://viaducthistory.com/history.htm
http://viaducthistory.com/neighborhood.htm#downtown
http://viaducthistory.com/history.htm ,
http://historylink.org/File/9925 , http://historylink.org/File/9951
https://twitter.com/BerthaDigsSR99
http://www.wsdot.wa.gov/Projects/Viaduct/Status/Blog/program-spotlight-tunnel%E2%80%99s-two-nerve-centers-taking-shape