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