Ilmakunnas, Pekka, Jan van Ours, Vegard Skirbekk, and Matthias Weiss. "Age and Working Capacity." Ageing, Health, and Productivity: The Economics of Increased Life Expectancy. : Oxford University Press, 2010-11-25. Oxford Scholarship Online. 2011-01-01. Date Accessed 21 May. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199587131.001.0001/acprof-9780199587131-chapter-13>.
Ilmakunnas, P., Ours, J., Skirbekk, V., & Weiss, M.(2010-11-25). Age and Working Capacity. In Ageing, Health, and Productivity: The Economics of Increased Life Expectancy. : Oxford University Press. Retrieved 21 May. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199587131.001.0001/acprof-9780199587131-chapter-13.
Ilmakunnas, Pekka, Jan van Ours, Vegard Skirbekk, and Matthias Weiss. "Age and Working Capacity." In Ageing, Health, and Productivity: The Economics of Increased Life Expectancy. : Oxford University Press, 2010-11-25. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199587131.001.0001/acprof-9780199587131-chapter-13.
Ilmakunnas P, Ours Jv, Skirbekk V, Weiss M. Age and Working Capacity. In: Garibaldi P, Oliveira Martins J, van Ours J. Ageing, Health, and Productivity: The Economics of Increased Life Expectancy. Oxford University Press; 2010. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780199587131.001.0001/acprof-9780199587131-chapter-13. Accessed May 21, 2013.