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 [QuickCheck: A Lightweight Tool for Random Testing of Haskell Programs](http://www.cs.tufts.edu/~nr/cs257/archive/john-hughes/quick.pdf)
 
-[QuickCheck Testing for Fun and Profit](http://people.inf.elte.hu/center/fulltext.pdf)
+[QuickCheck Testing for Fun and Profit](https://web.archive.org/web/20230912215719/http://people.inf.elte.hu/center/fulltext.pdf)
 
 Property-Based Testing, best explained in John Hughes own talk at [Testing the Hard Stuff and Staying Sane](https://www.youtube.com/watch?v=zi0rHwfiX1Q&list=PLZdCLR02grLp__wRg5OTavVj4wefg69hM).