"WHO / International Classification of Health Interventions (ICHI)". World Health Organization. Retrieved 2011-06-14. https://www.who.int/classifications/ichi/en/
"CCI to replace ICD-9 in Canada". CODING AND BILLING SALARY. May 9, 2016. http://codingandbillingsalary.com/cci-replace-icd-9-canada/
"CNC - NIC Overview | College of Nursing - The University of Iowa". nursing.uiowa.edu. https://nursing.uiowa.edu/cncce/nursing-interventions-classification-overview
ccam.sante.fr Archived October 16, 2005, at the Wayback Machine http://www.ccam.sante.fr/
"Home". http://systems.hscic.gov.uk/data/clinicalcoding/codingstandards/opcs4
fhs.usyd.edu.au Archived June 20, 2005, at the Wayback Machine http://www3.fhs.usyd.edu.au/ncchwww/site/4.1.3.htm