O6/09: http://www.nationaljewish.org/healthinfo/conditions/copd/lifestyle-management/bring-up-mucus.aspx.
http://www.cff.org/treatments/therapies/respiratory/airwayclearance/#High-frequency_Chest_Wall_Oscillation.
http://www.rtmagazine.com/issues/articles/2007-11_03.asp.
http://wishard.kramesonline.com/healthsheets/3,S,87545.
http://www3.nbnet.nb.ca/normap/autodrng.htm.
http://www.uwhealth.org/uwcysticfibrosiscenter/cysticfibrosiscftreatmentpositiveexpiratorypressurepep/13792.