https://books.chessbase.com/en/fortresses-you-should-know/fortress-or-not-a-fortress 2024-09-16 https://books.chessbase.com/en/fortresses-you-should-know/introduction 2024-09-20 https://books.chessbase.com/en/fortresses-you-should-know/extra-piece 2024-09-16 https://books.chessbase.com/en/fortresses-you-should-know/queen-pawn-vs-rook-and-pawn-part-1 2024-09-16 https://books.chessbase.com/en/fortresses-you-should-know/queen-vs-rook-and-pawn-part-2-plus-queen-vs-2 2024-09-16 https://books.chessbase.com/en/fortresses-you-should-know/rook-and-pawn-vs-bishop 2024-09-16 https://books.chessbase.com/en/fortresses-you-should-know/database 2024-09-16