1. HDRUK Phenotype Library. https://phenotypes.healthdatagateway.org/
2. ICD-9-CM Diagnostic Codes to SNOMED CT Map. https://www.nlm.nih.gov/research/umls/mapping_projects/icd9cm_to_snomedct.html
3. ICD-9-CM to and from ICD-10-CM and ICD-10-PCS General Equivalence Mappings. https://www.nber.org/research/data/icd-9-cm-and-icd-10-cm-and-icd-10-pcs-crosswalk-or-general-equivalence-mappings
4. OpenCodelists. https://www.opencodelists.org/
5. CORECT-R Data Coding v1.0 (2020). https://www.ndph.ox.ac.uk/corectr/files/corect-r-data-coding-v1-0-oct20.pdf