US site for HS codes: https://hts.usitc.gov/
UK site for HS codes (NI): https://www.trade-tariff.service.gov.uk/xi/sections
CA site for HS codes: https://www.cbsa-asfc.gc.ca/.../2021/html/tblmod-2-eng.html
AUS site for HS codes: https://www.abf.gov.au/importing.../tariff-classification
General Rules of interpretation: https://www.cbsa-asfc.gc.ca/trade-commerce/tariff-tarif/2021/html/rules-regles-3-eng.html