ARIA resources

W3C Resources

WAI Resources: https://www.w3.org/WAI/Resources/Overview

WCAG 2.0: https://www.w3.org/TR/WCAG20/

WCAG 2.1: https://www.w3.org/TR/WCAG21/

AODA (Accessibility for Ontarians with Disabilities Act): https://accessontario.com/aoda/

There are a number of great books on the topic of Web Accessibility. Here are a few of the better ones: