diff --git a/mkdocs.yml b/mkdocs.yml
index dabd0d1bbcf5f1dac1cef15c96345040a600f10c..765dca78df3a89834cef1d9036716def519b2731 100644
--- a/mkdocs.yml
+++ b/mkdocs.yml
@@ -13,6 +13,7 @@ nav:
   - Operators in quantum mechanics: '5_operators_QM.md'
   - Eigenvectors and eigenvalues: '6_eigenvectors_QM.md'
   - Differential equations 1: '7_differential_equations_1.md'
+  - Differential equations 2: '8_differential_equations_2.md'
 
 theme:
   name: material
diff --git a/src/differential_equations_2.md b/src/8_differential_equations_2.md
similarity index 99%
rename from src/differential_equations_2.md
rename to src/8_differential_equations_2.md
index a2d732cf072b82500b2b7e03925fa9f582a053d8..96e9eaf402f52bfa02e37755b357e12b5edfd016 100644
--- a/src/differential_equations_2.md
+++ b/src/8_differential_equations_2.md
@@ -574,4 +574,4 @@ necessary to work with numerical methods of solution.
         (a) Lf = A(x) \frac{d^2 f}{dx^2}
 
         (b) Lf = \frac{d}{dx} \big{()} A(x) \frac{df}{dx} \big{)}
-    
\ No newline at end of file
+