1. http://www.businessweek.com/investor/content/apr2006/pi20060421_378143.htm.
2. Kristoffersen S. Improved fatigue performance of threaded drillstring connections by cold rolling. PhD thesis, Norwegian University of Science and Technology, Norway, ISBN 82-421-5402-1; 2002.
3. Macdonald KA. Fatigue of drillstring threaded connections. PhD thesis, University of Aberdeen, UK; 1996.
4. API Specification 5D, Specification for drill pipe. 5th ed.; October 2001.
5. API Specification 7, Specification for rotary drill stem elements. 40th ed.; 2001.