References

(1) Sleep stages. (2000). Retrieved from http://s.hswstatic.com/gif/sleep-stages.gif
(2) ‘Electroencephalography’ At: Society for Neuroscience (2015). Brain Facts. A primer on the brain and nervous system.
(3) Inchon Kobi Medical Center. Sleep cycle. Retrieved from http://www.bettersleep.co.kr/wp-content/uploads/2015/02/sleep-cycle-11.jpg
(4) Häggström, M. (2009). Complications of insomnia. Retrieved from https://upload.wikimedia.org/wikipedia/commons/thumb/c/c6/Complications_of_insomnia.svg/2000px-Complications_of_insomnia.svg.png
(5) Sleep apnea. Retrieved from http://sspi.com/wp-content/uploads/2013/04/blocked-airway-example-pic.png
(6) Paquet, D. ‘Normal Vs Narcoleptic Sleep Pattern’. Retrieved from http://thebrain.mcgill.ca/flash/a/a_11/a_11_p/a_11_p_cyc/a_11_p_cyc_4a.jpg