HELMER, R. G. (1991). Time Management For Engineers And Constructors Ray G. Helmer. American Society of Civil Engi.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रHELMER, Ray Gray. Time Management For Engineers And Constructors Ray G. Helmer. American Society of Civil Engi, 1991.
एमएलए (8वां संस्करण) प्रशस्ति पत्रHELMER, Ray Gray. Time Management For Engineers And Constructors Ray G. Helmer. American Society of Civil Engi, 1991.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.