The major part of the material on which the Grünfeld Defence Powerbook 2019 is based comes from the engine room of playchess.com: 219 000 games. To this imposing mass we have added another 60 000 games from Mega and from correspondence chess.
The Pirc Defence Powerbook 2019 (including the Modern Defence) consists for a greater part of engine games (160 000), to which has been added high value material from Mega and the Correspondence Database (46 000).
The Queen's Indian Powerbook 2019 has a tree structure which is based on a mixture of over 350 000 complete chess games played in the Engine room of playchess.com and the best games played by humans (50 000).
The major part of the material on which the Sicilian Kalashnikov Powerbook 2019 is based comes from the engine room of playchess.com: approximately 18 000 games. To these have been added another 4500 games from the Mega database and from correspondence ch