hxxps://validator[.]schema[.]org/

hxxps://github[.]com/schemaorg/schemaorg/issues?q=is%3Aissue+is%3Aopen+Offer

hxxp://www[.]gs1[.]org/barcodes/technical/idkeys/gtin

hxxp://www[.]gs1[.]org/barcodes/support/check_digit_calculator

hxxp://www[.]gs1us[.]org/resources/standards/gtin-validation-guide

hxxp://www[.]gs1[.]org/

hxxps://en[.]wikipedia[.]org/wiki/Amazon_Standard_Identification_Number

hxxps://www[.]gs1[.]org/standards/id-keys/gtin

hxxps://www[.]gs1[.]org/standards/Digital-Link/

hxxps://github[.]com/schemaorg/schemaorg/issues/3156#issuecomment-1209522809

hxxps://www[.]gs1[.]org/services/check-digit-calculator

hxxps://en[.]wikipedia[.]org/wiki/Global_Trade_Item_Number

hxxps://en[.]wikipedia[.]org/wiki/Responsive_web_design

hxxp://en[.]wikipedia[.]org/wiki/ISO_4217

hxxps://en[.]wikipedia[.]org/wiki/List_of_cryptocurrencies

hxxps://en[.]wikipedia[.]org/wiki/Local_exchange_trading_system

hxxp://en[.]wikipedia[.]org/wiki/Dollar_sign#Currencies_that_use_the_dollar_or_peso_sign

hxxp://www[.]w3[.]org/TR/xhtml-rdfa-primer/#using-the-content-attribute

hxxp://blog[.]schema[.]org/2012/11/good-relations-and-schemaorg[.]html

hxxp://purl[.]org/goodrelations/

hxxps://en[.]wikipedia[.]org/wiki/Microdata_(HTML)

hxxps://en[.]wikipedia[.]org/wiki/RDFa

hxxps://en[.]wikipedia[.]org/wiki/JSON-LD