Universal Rating System - URS

Elo rating system - Wikipedia

Which countries have the most inflated Elo ratings?

In chess.com users have a rating. What is this? Is this connected to a wider chess rating? How can one's rating level be interpreted, and what is a passably good rating?

Chess Rankings & Leaderboards - Chess Terms

Chess Ratings - Chess Terms

Visualizing FIDE chess rating list

How to look up your US Chess rating – Indermaur Chess Foundation

▷ Elo rank chess: Learn about the #1 system for rated strong

Elo rating system: Common link between Facemash and chess

Elo and Glicko Standardised Rating Systems – TOM ROCKS MATHS