Matthys, Robert James. "Pendulum rod materials." Accurate Clock Pendulums. : Oxford University Press, 2004-06-03. Oxford Scholarship Online. 2010-01-01. Date Accessed 23 May. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780198529712.001.0001/acprof-9780198529712-chapter-21>.
Matthys, R.(2004-06-03). Pendulum rod materials. In Accurate Clock Pendulums. : Oxford University Press. Retrieved 23 May. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780198529712.001.0001/acprof-9780198529712-chapter-21.
Matthys, Robert James. "Pendulum rod materials." In Accurate Clock Pendulums. : Oxford University Press, 2004-06-03. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780198529712.001.0001/acprof-9780198529712-chapter-21.
Matthys RJ. Pendulum rod materials. In: Matthys RJ. Accurate Clock Pendulums. Oxford University Press; 2004. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780198529712.001.0001/acprof-9780198529712-chapter-21. Accessed May 23, 2013.