Independent Petroleum Association of America. The Oil producing industry in your state. Petroleum Independent Publishers.
Παραπομπή σε μορφή Chicago (17η εκδ.)Independent Petroleum Association of America. The Oil Producing Industry in Your State. [Washington: Petroleum Independent Publishers.
Παραπομπή σε μορφή MLA (8th εκδ.)Independent Petroleum Association of America. The Oil Producing Industry in Your State. Petroleum Independent Publishers.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.