The theorem provers page has a link for Ivor at the bottom: http://www.haskell.org/haskellwiki/Libraries_and_tools/Theorem_provers

This current link is dead: http://www.dcs.st-and.ac.uk/~eb/ivor.php

This new link works: http://eb.host.cs.st-andrews.ac.uk/ivor.php

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 - EJR