Beating the Bludgers – A Study of Defensive Strategies in Quidditch is a Quidditch handbook. It is one of the previous works by author Kenilworthy Whisp, mentioned in the opening section of Quidditch through the Ages (QA).
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From the Web
The Rowling Library, TRL Magazine Issue #56: Harry Potter Loves Books: The Books in the Harry Potter Series by Oliver Horton
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Harry Potter Wiki: Beating the Bludgers - A Study of Defensive Strategies in Quidditch