"Purpose of the ATC/DDD system". WHO Collaborating Centre for Drug Statistics Methodology. Archived from the original on 14 January 2010. Retrieved 6 July 2021.
"ATC/DDD Methodology: History". WHO Collaborating Centre for Drug Statistics Methodology. Archived from the original on 2010-03-14. Retrieved 2009-12-26.
"New ATC 5th levels". WHO Collaborating Centre for Drug Statistics Methodology. 2021-05-04. Archived from the original on 2021-11-28. Retrieved 2021-06-18.
"ATC Index with DDDs". WHO Collaborating Centre for Drug Statistics Methodology. 2020-12-16. Archived from the original on 2020-05-23. Retrieved 2020-06-15.
"Purpose of the ATC/DDD system". WHO Collaborating Centre for Drug Statistics Methodology. Archived from the original on 14 January 2010. Retrieved 6 July 2021.
"ATC/DDD Methodology: History". WHO Collaborating Centre for Drug Statistics Methodology. Archived from the original on 2010-03-14. Retrieved 2009-12-26.
"New ATC 5th levels". WHO Collaborating Centre for Drug Statistics Methodology. 2021-05-04. Archived from the original on 2021-11-28. Retrieved 2021-06-18.
"ATC Index with DDDs". WHO Collaborating Centre for Drug Statistics Methodology. 2020-12-16. Archived from the original on 2020-05-23. Retrieved 2020-06-15.