Não informado. (1944). Drilling contractor. American Association of Oilwell Drilling Contractors.
Chicago-referens (17:e uppl.)Não informado. Drilling Contractor. Dallas, Tex: American Association of Oilwell Drilling Contractors, 1944.
MLA-referens (8:e uppl.)Não informado. Drilling Contractor. American Association of Oilwell Drilling Contractors, 1944.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.