APA
Heller P. R., Unu Wider, . (2017). Doubling down: National oil companies as instruments of risk. Helsinki: UNU-WIDER.
Chicago
Heller Patrick R.P, Unu Wider, . 2017. Doubling down: National oil companies as instruments of risk. Helsinki: UNU-WIDER.
Harvard
Heller P. R., Unu Wider, . (2017). Doubling down: National oil companies as instruments of risk. Helsinki: UNU-WIDER.
MLA
Heller Patrick R.P, Unu Wider, . Doubling down: National oil companies as instruments of risk. Helsinki: UNU-WIDER. 2017.