The major part of the material on which the Sicilian Dragon Powerbook 2022 is based comes from the engine room of playchess.com: 161 000 games. There have been added another 14000 games from Mega and from correspondence chess.
The Powerbook Unusual Lines 2022 is based on more than 700,000 games of the ECO codes A00-A09, i.e. it deals with all opening beginnings other than 1.e4, 1.d4 as well as 1.c4.
Most of the material on which the Sicilian Paulsen Powerbook 2022 is based comes from the engine room of Schach.de: 426,000 games. In addition to this impressive amount, there are 43,000 games from the Mega and from correspondence chess.
The major part of the material on which the Grünfeld Defence Powerbook 2021 is based comes from the engine room of playchess.com: 232 000 games. To this imposing mass we have added another 70 000 games from Mega and from correspondence chess.
For the Slav and Semi-Slav Powerbook 2021 the ratings average was set at 2400. 1.76 million games from the engine room of playchess.com met this threshold, to which were added over 80 000 games played by humans.
