• American Gas Association

http://www.aga.org

• Call Before You Dig (Connecticut)

http://www.cbyd.com

• Common Ground Alliance

http://www.commongroundalliance.com

• Interstate Natural Gas Association
  of America (INGAA)

http://ingaa.org

• Dig Safely (New York)

http://www.digsafelynewyork.com

• Dig Safely NYC (New York
  City/Long Island)

http://www.ocuc.net

• National Pipeline Mapping System

http://www.npms.rspa.dot.gov

• Northeast Gas Association

http://www.northeastgas.org

• Office of Pipeline Safety

http://www.phmsa.dot.gov

• Transportation Safety Institute

http://www.tsi.gov