Liben, Stephen. "Breathlessness in children." Dyspnoea in Advanced Disease: A guide to clinical management. : Oxford University Press, 2005-11-24. Oxford Scholarship Online. 2011-11-17. Date Accessed 19 May. 2013 <http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780198530039.001.0001/acprof-9780198530039-chapter-7>.
Liben, S.(2005-11-24). Breathlessness in children. In Dyspnoea in Advanced Disease: A guide to clinical management. : Oxford University Press. Retrieved 19 May. 2013, from http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780198530039.001.0001/acprof-9780198530039-chapter-7.
Liben, Stephen. "Breathlessness in children." In Dyspnoea in Advanced Disease: A guide to clinical management. : Oxford University Press, 2005-11-24. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780198530039.001.0001/acprof-9780198530039-chapter-7.
Liben S. Breathlessness in children. In: Booth S, Dudgeon D. Dyspnoea in Advanced Disease: A guide to clinical management. Oxford University Press; 2005. http://www.oxfordscholarship.com/view/10.1093/acprof:oso/9780198530039.001.0001/acprof-9780198530039-chapter-7. Accessed May 19, 2013.