Logic 1st edition as PDF, Seven Bridges Press and CSLI, 1999. External links Fitch's Paradox of Knowability An online Java application for proof building A Web implementation of Fitch proof system (propositional and first-order) at proofmod.mindconnect.cc The Jape general-purpose proof assistant (see Jape) Resources for typesetting proofs in Fitch notation with LaTeX (see LaTeX) FitchJS: An open source web app to construct proofs in Fitch notation (and export to LaTeX) Natural deduction proof editor and checker in Fitch notation Philosophical logic Logical calculi