Usman. Nigerian Oil and Gas Industry Laws. Malthouse Press.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रUsman. Nigerian Oil and Gas Industry Laws. Malthouse Press.
एमएलए (9वां संस्करण) प्रशस्ति पत्रUsman. Nigerian Oil and Gas Industry Laws. Malthouse Press.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.