"Pneumatica: Section 50 – The Steam Engine" from The Pneumatics of Hero of Alexandria (1st century AD), translated from the original Greek by Bennet Woodcroft (Professor of Machinery in University College London) published 1851 by Taylor Walton and Maberly (London) – online edition[リンク切れ] accessed 2009-07-03
uchicago.edu
penelope.uchicago.edu
"デ・アーキテクチュラ De Architectura": Chapter VI (paragraph 2) from "Ten Books on Architecture" by Vitruvius (1st century BC), translated by Bill Thayer, published 17, June, 08 [1] accessed 2009-07-07