"Deep well drilling. "; "Gray, A. R."; "Oil well drilling.", "Boring.", "Gas well drilling.", "Wells."; "Gray, A. R."; "1917"; "Journal article tearout from: Natural Gas Association of America. Meeting. Proceedings, 12th (1917). "; ""; "P752"; "pec"; "Boring.", "Gas well drilling.", "Oil well drilling.", "Wells."; "14256"; .