APA
Hjelde E., World Petroleum Congress (17th. : 2002 sept. 1-5 : Río de Janeiro B., .Frigg field decommissioning. : .
Chicago
Hjelde Erik, World Petroleum Congress (17th. : 2002 sept. 1-5 : Río de Janeiro Brasil), .Frigg field decommissioning. : .
Harvard
Hjelde E., World Petroleum Congress (17th. : 2002 sept. 1-5 : Río de Janeiro B., .Frigg field decommissioning. : .
MLA
Hjelde Erik, World Petroleum Congress (17th. : 2002 sept. 1-5 : Río de Janeiro Brasil), .: . .