Não informado. (1944). Drilling contractor. American Association of Oilwell Drilling Contractors.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Drilling Contractor. Dallas, Tex: American Association of Oilwell Drilling Contractors, 1944.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Drilling Contractor. American Association of Oilwell Drilling Contractors, 1944.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.