Understanding Test Rules for WCAG 2 Success Criteria| www.w3.org
Technique G195:Using an author-supplied, visible focus indicator| www.w3.org
Technique G165:Using the default focus indicator for the platform so that high visibility default focus indicators will carry over| www.w3.org
Understanding Techniques for WCAG 2.1 Success Criteria| www.w3.org
Accessibility resources free online from the international standards organization: W3C Web Accessibility Initiative (WAI).| Web Accessibility Initiative (WAI)