Small Encyclopedia of Chess Openings ABCDE on CD (3rd Edition)

Encyclopaedia of Chess Openings BI

Chess Opening Database - Chess Forums

learning - Where can I find free training tools like detailed annotated chess openings, middle games and endgames in the PGN format? - Chess Stack Exchange

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Announcements by Opening Master

How do I use the Game Explorer? - Chess.com Member Support and FAQs

Deal of the Week: Opening Tutorials 1 to 5 for just 29.90 EUR

Chessify on X: Chess databases offer you multiple benefits - opening stats, game search, opponent info - and Chessify offers the biggest online database with weekly updates coming automatically. 😉 You will

Opening repertoire study with spaced repetition (+ database and game collections) - Chess Forums

The most common opening in master games (according to chess.com's database) is surprisingly the Open Sicilian, with e4 c6 being almost 3x more popular than e4 e5. : r/chess