* Marshall, Thomas H. (1925), ''James Watt'', [http://www.history.rochester.edu/steam/marshall/chapter3.html Chapter 3: Mathematical Instrument Maker], from [http://www.history.rochester.edu/steam Steam Engine Library] of [[University of Rochester]] Department of History.

* Marshall, Thomas H. (1925) [http://www.history.rochester.edu/steam/marshall/ ''James Watt''], [[University of Rochester]] Department of History.