In the U.S., What Resources are Authoritative for Accessibility?
Authoritative Resources are those implementing the Rules and Standards.
Methods and products following the guidance provided by Adobe, AIIM, Apple, Government Agencies (DHS, HHS, VA, GSA ITAW), Microsoft, PDF/UA, and W3C.
Techniques supporting the PDF Association's Matterhorn Protocol, W3C's WAI and WCAG, and methods recommended by WebAIM.
Validation tools provided by commercial companies following the PDF/UA and W3C guidelines which include the PDF Association's Matterhorn Protocol implementations tools:
PACv2 and the Validator
DHS Trusted Tester methods