Hills, vol 3, pp. 13 "Some Unpublished Letters of James Watt" in Journal of Institution of Mechanical Engineers (London, 1915).
Marrë më 25 March 2011.  ^ Hills, vol 3, pp. 13 "Disa Pabotuar Letra e James Watt" në Ditarin e Institucionit të inxhinjerë (Londër, 1915).