diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -33,56 +33,56 @@ Status of the chapters:
   - :tada: chapter is completely formalized (possibly excluding the Appendix)
 
 ### Number Theory
-  1. :speech_balloon: [Six proofs of the infinity of primes](/FormalBook/Ch01_Six_proofs_of_the_infinity_of_primes.lean)
-  2. :speech_balloon: [Bertrand's postulate](/FormalBook/Ch02_Bertrand's_postulate.lean)
-  3. :speech_balloon: [Binomial coefficients are (almost) never powers](/FormalBook/Ch03_Binomial_coefficients_are_(almost)_never_powers.lean)
-  4. :x: [Representing numbers as sums of two squares](/FormalBook/Ch04_Representing_numbers_as_sums_of_two_squares.lean)
-  5. :thought_balloon: [The law of quadratic reciprocity](/FormalBook/Ch05_The_law_of_quadratic_reciprocity.lean)
-  6. :thought_balloon: [Every finite division ring is a field](/FormalBook/Ch06_Every_finite_division_ring_is_a_field.lean)
-  7. :thought_balloon: [The spectral theorem and Hadamard's determinant problem](/FormalBook/Ch07_The_spectral_theorem_and_Hadamard's_determinant_problem.lean)
-  8. :thought_balloon: [Some irrational numbers](/FormalBook/Ch08_Some_irrational_numbers.lean)
-  9. :x: [Four times ](/FormalBook/Ch09_Four_times_pi²_over_6.lean)$\pi^2/6$
+  1. :speech_balloon: [Six proofs of the infinity of primes](formal_book/blob/main/FormalBook/Ch01_Six_proofs_of_the_infinity_of_primes.lean)
+  2. :speech_balloon: [Bertrand's postulate](formal_book/blob/main/FormalBook/Ch02_Bertrand's_postulate.lean)
+  3. :speech_balloon: [Binomial coefficients are (almost) never powers](formal_book/blob/main/FormalBook/Ch03_Binomial_coefficients_are_(almost)_never_powers.lean)
+  4. :x: [Representing numbers as sums of two squares](formal_book/blob/main/FormalBook/Ch04_Representing_numbers_as_sums_of_two_squares.lean)
+  5. :thought_balloon: [The law of quadratic reciprocity](formal_book/blob/main/FormalBook/Ch05_The_law_of_quadratic_reciprocity.lean)
+  6. :thought_balloon: [Every finite division ring is a field](formal_book/blob/main/FormalBook/Ch06_Every_finite_division_ring_is_a_field.lean)
+  7. :thought_balloon: [The spectral theorem and Hadamard's determinant problem](formal_book/blob/main/FormalBook/Ch07_The_spectral_theorem_and_Hadamard's_determinant_problem.lean)
+  8. :thought_balloon: [Some irrational numbers](formal_book/blob/main/FormalBook/Ch08_Some_irrational_numbers.lean)
+  9. :x: [Four times ](formal_book/blob/main/FormalBook/Ch09_Four_times_pi²_over_6.lean)$\pi^2/6$
 
 ### Geometry
-  10. :x: [Hilbert's third problem: decomposing polyhedra](/FormalBook/Ch10_Hilbert's_third_problem_decomposing_polyhedra.lean)
-  11. :x: [Lines in the plane and decompositions of graphs](/FormalBook/Ch11_Lines_in_the_plane_and_decompositions_of_graphs.lean)
-  12. :x: [The slope problem](/FormalBook/Ch12_The_slope_problem.lean)
-  13. :x: [Three applications of Euler's formula](/FormalBook/Ch13_Three_applications_of_Euler's_formula.lean)
-  14. :x: [Cauchy's rigidity theorem](/FormalBook/Ch14_Cauchy's_rigidity_theorem.lean)
-  15. :x: [The Borromean rings don't exist](/FormalBook/Ch15_The_Borromean_rings_don't_exist.lean)
-  16. :x: [Touching simplices](/FormalBook/Ch16_Touching_simplices.lean)
-  17. :x: [Every large point set has an obtuse angle](/FormalBook/Ch17_Every_large_point_set_has_an_obtuse_angle.lean)
-  18. :x: [Borsuk's conjecture](/FormalBook/Ch18_Borsuk's_conjecture.lean)
+  10. :x: [Hilbert's third problem: decomposing polyhedra](formal_book/blob/main/FormalBook/Ch10_Hilbert's_third_problem_decomposing_polyhedra.lean)
+  11. :x: [Lines in the plane and decompositions of graphs](formal_book/blob/main/FormalBook/Ch11_Lines_in_the_plane_and_decompositions_of_graphs.lean)
+  12. :x: [The slope problem](formal_book/blob/main/FormalBook/Ch12_The_slope_problem.lean)
+  13. :x: [Three applications of Euler's formula](formal_book/blob/main/FormalBook/Ch13_Three_applications_of_Euler's_formula.lean)
+  14. :x: [Cauchy's rigidity theorem](formal_book/blob/main/FormalBook/Ch14_Cauchy's_rigidity_theorem.lean)
+  15. :x: [The Borromean rings don't exist](formal_book/blob/main/FormalBook/Ch15_The_Borromean_rings_don't_exist.lean)
+  16. :x: [Touching simplices](formal_book/blob/main/FormalBook/Ch16_Touching_simplices.lean)
+  17. :x: [Every large point set has an obtuse angle](formal_book/blob/main/FormalBook/Ch17_Every_large_point_set_has_an_obtuse_angle.lean)
+  18. :x: [Borsuk's conjecture](formal_book/blob/main/FormalBook/Ch18_Borsuk's_conjecture.lean)
 ### Analysis
-  19. :x: [Sets, functions, and the continuum hypothesis](/FormalBook/Ch19_Sets,_functions,_and_the_continuum_hypothesis.lean)
-  20. :thought_balloon: [In praise of inequalities](/FormalBook/Ch20_In_praise_of_inequalities.lean)
-  21. :thought_balloon: [The fundamental theorem of algebra](/FormalBook/Ch21_The_fundamental_theorem_of_algebra.lean)
-  22. :x: [One square and an odd number of triangles](/FormalBook/Ch22_One_square_and_an_odd_number_of_triangles.lean)
-  23. :x: [A theorem of Pólya on polynomials](/FormalBook/Ch23_A_theorem_of_Pólya_on_polynomials.lean)
-  24. :x: [Van der Waerden's permanent conjecture](/FormalBook/Ch24_Van_der_Waerden's_permanent_conjecture.lean)
-  25. :x: [On a lemma of Littlewook and Offord](/FormalBook/Ch25_On_a_lemma_of_Littlewook_and_Offord.lean)
-  26. :x: [Cotangent and the Herglotz trick](/FormalBook/Ch26_Cotangent_and_the_Herglotz_trick.lean)
-  27. :x: [Buffon's needle problem](/FormalBook/Ch27_Buffon's_needle_problem.lean)
+  19. :x: [Sets, functions, and the continuum hypothesis](formal_book/blob/main/FormalBook/Ch19_Sets,_functions,_and_the_continuum_hypothesis.lean)
+  20. :thought_balloon: [In praise of inequalities](formal_book/blob/main/FormalBook/Ch20_In_praise_of_inequalities.lean)
+  21. :thought_balloon: [The fundamental theorem of algebra](formal_book/blob/main/FormalBook/Ch21_The_fundamental_theorem_of_algebra.lean)
+  22. :x: [One square and an odd number of triangles](formal_book/blob/main/FormalBook/Ch22_One_square_and_an_odd_number_of_triangles.lean)
+  23. :x: [A theorem of Pólya on polynomials](formal_book/blob/main/FormalBook/Ch23_A_theorem_of_Pólya_on_polynomials.lean)
+  24. :x: [Van der Waerden's permanent conjecture](formal_book/blob/main/FormalBook/Ch24_Van_der_Waerden's_permanent_conjecture.lean)
+  25. :x: [On a lemma of Littlewook and Offord](formal_book/blob/main/FormalBook/Ch25_On_a_lemma_of_Littlewook_and_Offord.lean)
+  26. :x: [Cotangent and the Herglotz trick](formal_book/blob/main/FormalBook/Ch26_Cotangent_and_the_Herglotz_trick.lean)
+  27. :x: [Buffon's needle problem](formal_book/blob/main/FormalBook/Ch27_Buffon's_needle_problem.lean)
 ### Combinatorics
-  28. :x: [Pigeon-hole and double counting](/FormalBook/Ch28_Pigeon-hole_and_double_counting.lean)
-  29. :x: [Tiling rectangles](/FormalBook/Ch29_Tiling_rectangles.lean)
-  30. :x: [Three famous theorems on finite sets](/FormalBook/Ch30_Three_famous_theorems_on_finite_sets.lean)
-  31. :x: [Shuffling cards](/FormalBook/Ch31_Shuffling_cards.lean)
-  32. :thought_balloon: [Lattice paths and determinants](/FormalBook/Ch32_Lattice_paths_and_determinants.lean)
-  33. :x: [Cayley's formula for the number of trees](/FormalBook/Ch33_Cayley's_formula_for_the_number_of_trees.lean)
-  34. :x: [Identities versus bijections](/FormalBook/Ch34_Identities_versus_bijections.lean)
-  35. :x: [The finite Kakeya problem](/FormalBook/Ch35_The_finite_Kakeya_problem.lean)
-  36. :x: [Completing Latin squares](/FormalBook/Ch36_Completing_Latin_squares.lean)
+  28. :x: [Pigeon-hole and double counting](formal_book/blob/main/FormalBook/Ch28_Pigeon-hole_and_double_counting.lean)
+  29. :x: [Tiling rectangles](formal_book/blob/main/FormalBook/Ch29_Tiling_rectangles.lean)
+  30. :x: [Three famous theorems on finite sets](formal_book/blob/main/FormalBook/Ch30_Three_famous_theorems_on_finite_sets.lean)
+  31. :x: [Shuffling cards](formal_book/blob/main/FormalBook/Ch31_Shuffling_cards.lean)
+  32. :thought_balloon: [Lattice paths and determinants](formal_book/blob/main/FormalBook/Ch32_Lattice_paths_and_determinants.lean)
+  33. :x: [Cayley's formula for the number of trees](formal_book/blob/main/FormalBook/Ch33_Cayley's_formula_for_the_number_of_trees.lean)
+  34. :x: [Identities versus bijections](formal_book/blob/main/FormalBook/Ch34_Identities_versus_bijections.lean)
+  35. :x: [The finite Kakeya problem](formal_book/blob/main/FormalBook/Ch35_The_finite_Kakeya_problem.lean)
+  36. :x: [Completing Latin squares](formal_book/blob/main/FormalBook/Ch36_Completing_Latin_squares.lean)
 ### Graph Theory
-  37. :x: [Permanents and the power of entropy](/FormalBook/Ch37_Permanents_and_the_power_of_entropy.lean)
-  38. :x: [The Dinitz problem](/FormalBook/Ch38_The_Dinitz_problem.lean)
-  39. :x: [Five-coloring plane graphs](/FormalBook/Ch39_Five-coloring_plane_graphs.lean)
-  40. :x: [How to guard a museum](/FormalBook/Ch40_How_to_guard_a_museum.lean)
-  41. :x: [Turán's graph theorem](/FormalBook/Ch41_Turán's_graph_theorem.lean)
-  42. :x: [Communicating without errors](/FormalBook/Ch42_Communicating_without_errors.lean)
-  43. :x: [The chromatic number of Kneser graphs](/FormalBook/Ch43_The_chromatic_number_of_Kneser_graphs.lean)
-  44. :speech_balloon: [Of friends and politicians](/FormalBook/Ch44_Of_friends_and_politicians.lean)
-  45. :thought_balloon: [Probability makes counting (sometimes) easy](/FormalBook/Ch45_Probability_makes_counting_(sometimes)_easy.lean)
+  37. :x: [Permanents and the power of entropy](formal_book/blob/main/FormalBook/Ch37_Permanents_and_the_power_of_entropy.lean)
+  38. :x: [The Dinitz problem](formal_book/blob/main/FormalBook/Ch38_The_Dinitz_problem.lean)
+  39. :x: [Five-coloring plane graphs](formal_book/blob/main/FormalBook/Ch39_Five-coloring_plane_graphs.lean)
+  40. :x: [How to guard a museum](formal_book/blob/main/FormalBook/Ch40_How_to_guard_a_museum.lean)
+  41. :x: [Turán's graph theorem](formal_book/blob/main/FormalBook/Ch41_Turán's_graph_theorem.lean)
+  42. :x: [Communicating without errors](formal_book/blob/main/FormalBook/Ch42_Communicating_without_errors.lean)
+  43. :x: [The chromatic number of Kneser graphs](formal_book/blob/main/FormalBook/Ch43_The_chromatic_number_of_Kneser_graphs.lean)
+  44. :speech_balloon: [Of friends and politicians](formal_book/blob/main/FormalBook/Ch44_Of_friends_and_politicians.lean)
+  45. :thought_balloon: [Probability makes counting (sometimes) easy](formal_book/blob/main/FormalBook/Ch45_Probability_makes_counting_(sometimes)_easy.lean)
 
 ## Contributing