Frank, H. J. (1966). Crude oil prices in the Middle East: A study in oligopolistic price behavior. Praeger.
Παραπομπή σε μορφή Chicago (17η εκδ.)Frank, Helmut Jack. Crude Oil Prices in the Middle East: A Study in Oligopolistic Price Behavior. New York: Praeger, 1966.
Παραπομπή σε μορφή MLA (9th εκδ.)Frank, Helmut Jack. Crude Oil Prices in the Middle East: A Study in Oligopolistic Price Behavior. Praeger, 1966.