APA

Ahlbrandt T. S., Klett T., United States Geological Survey, World Petroleum Congress (15th. : 1997 : Beijing), Klett T. & United States Geological Survey.Estimates of undiscoveres oil and gas in petroleum systems of the world. : .

Chicago

Ahlbrandt Thomas S, Klett T.R, United States Geological Survey, World Petroleum Congress (15th. : 1997 : Beijing), Klett T.R and United States Geological Survey.Estimates of undiscoveres oil and gas in petroleum systems of the world. : .

Harvard

Ahlbrandt T. S., Klett T., United States Geological Survey, World Petroleum Congress (15th. : 1997 : Beijing), Klett T. and United States Geological Survey.Estimates of undiscoveres oil and gas in petroleum systems of the world. : .

MLA

Ahlbrandt Thomas S, Klett T.R, United States Geological Survey, World Petroleum Congress (15th. : 1997 : Beijing), Klett T.R and United States Geological Survey.: . .