WKO: https://www.wko.at/
Gemeinde Hartkirchen: https://www.hartkirchen.ooe.gv.at
Gemeinde Tarsdorf: https://www.tarsdorf.at
Geologische Bundesanstalt: https://www.geologie.ac.at
Colossus Minerals: https://www.colossusminerals.com
Caldecott Tunnel: https://www.caldecott-tunnel.org
Digging on Caldecott Fourth Bore Now from Both Directions, Contra Costa Times

  03/17/11 - http://www.mercurynews.com/breaking-news/ci_17637535

Tunneling begins at Caldecott, YouTube/Contra Costa Times

03/17/11 - http://www.youtube.com/watch?v=5huoIkVSvKk

 Crews start tunneling on Oakland side of Caldecott, ABC 7/KGO TV

03/17/11 - http://abclocal.go.com/kgo/story?section=resources/traffic&id=8020029

Caldecott Tunnel: Methane traces add risk to dig, SF Chronicle

03/18/11 - http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/03/17/BAQ81IDVMC.DTL

 Major milestone in Caldecott Tunnel work, NBC Bay Area

03/17/11 - http://www.nbcbayarea.com/news/local/Major-Milestone-In-Caldecott-Tunnel-Work-118164959.html

 The Queen of the Road: Courteous drivers or “sheep” at the Caldecott Tunnel, Contra Costa Times

02/20/11 - http://www.contracostatimes.com/ci_17407371?source=most_viewed&nclick_check=1