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 ### Books
 
 - Types and Programming Languages by Benjamin C. Pierce
-- Functional Programming in Lean by David Thrane Christiansen
+- Functional Programming in Lean by David Thrane Christiansen (https://lean-lang.org/functional_programming_in_lean/)
 - Crafting Interpreters by Robert Nystrom (https://craftinginterpreters.com)
 - Certified Programming with Dependent Types by Adam Chlipala (http://adam.chlipala.net/cpdt/)
 - Essentials of Compilation by Jeremy G. Siek (https://github.com/IUCompilerCourse/Essentials-of-Compilation)