1. 2010 http://statcan.gc.ca/pub/82-625-x/2011001/article/11458-eng.htm
2. 2008 http://www.statcan.gc.ca/pub/82-003-x/2008002/article/10551-eng.pdf
3. 2004 http://www.ices.on.ca/file/Burden_of_Asthma_Aug-07.pdf
4. 2008 http://www.chd.dphe.state.co.us/Resources/adultdata/asthmaSurveillanceReport.pdf
5. 2010 http://www.mcanonline.org/files/ChangingpO2licyReport.pdf