diff --git a/config/en/mkdocs.yaml b/config/en/mkdocs.yaml
index 2772fb9..ef58daf 100755
--- a/config/en/mkdocs.yaml
+++ b/config/en/mkdocs.yaml
@@ -175,9 +175,6 @@ nav:
         - 'Lagrangian formalism': physics/classical-mechanics/lagrangian-mechanics/lagrangian-formalism.md
         - 'Lagrange equations': physics/classical-mechanics/lagrangian-mechanics/lagrange-equations.md
         - 'Lagrange generalizations': physics/classical-mechanics/lagrangian-mechanics/lagrange-generalizations.md
-        - 'Applications':
-          - 'Celestial mechanics': physics/classical-mechanics/lagrangian-mechanics/applications/celestial-mechanics.md
-          - 'Oscillations': physics/classical-mechanics/lagrangian-mechanics/applications/oscillations.md
       - 'Hamiltonian mechanics': 
         - 'Hamiltonian formalism': physics/classical-mechanics/hamiltonian-mechanics/hamiltonian-formalism.md
         - 'Equations of Hamilton': physics/classical-mechanics/hamiltonian-mechanics/equations-of-hamilton.md
@@ -187,7 +184,7 @@ nav:
       - 'Kerr geometry': physics/relativistic-mechanics/kerr-geometry.md
       - 'Wave geometry': physics/relativistic-mechanics/wave-geometry.md
 #    - 'Quantum mechanics':
-#    - 'Statistical mechanics'
+#    - 'Statistical mechanics':
     - 'Electromagnetism': 
 #      - 'Electrostatics':
 #      - 'Magnetostatics': 
diff --git a/config/nl/mkdocs.yaml b/config/nl/mkdocs.yaml
index f280975..7e46125 100755
--- a/config/nl/mkdocs.yaml
+++ b/config/nl/mkdocs.yaml
@@ -1,4 +1,4 @@
-site_name: Mijn aantekeningen
+site_name: Wiskunde en natuurkunde wiki
 docs_dir: '../../docs/nl'
 
 theme:
diff --git a/docs/en/physics/classical-mechanics/lagrangian-mechanics/applications/celestial-mechanics.md b/docs/en/physics/classical-mechanics/lagrangian-mechanics/applications/celestial-mechanics.md
deleted file mode 100644
index 60828c0..0000000
--- a/docs/en/physics/classical-mechanics/lagrangian-mechanics/applications/celestial-mechanics.md
+++ /dev/null
@@ -1 +0,0 @@
-# Celestial mechanics
\ No newline at end of file
diff --git a/docs/en/physics/classical-mechanics/lagrangian-mechanics/applications/oscillations.md b/docs/en/physics/classical-mechanics/lagrangian-mechanics/applications/oscillations.md
deleted file mode 100644
index 0443df6..0000000
--- a/docs/en/physics/classical-mechanics/lagrangian-mechanics/applications/oscillations.md
+++ /dev/null
@@ -1 +0,0 @@
-# Oscillations
\ No newline at end of file
diff --git a/docs/en/physics/classical-mechanics/newtonian-mechanics/momentum.md b/docs/en/physics/classical-mechanics/newtonian-mechanics/momentum.md
index f5a208a..f09ea27 100644
--- a/docs/en/physics/classical-mechanics/newtonian-mechanics/momentum.md
+++ b/docs/en/physics/classical-mechanics/newtonian-mechanics/momentum.md
@@ -1 +1,30 @@
-# Momentum
\ No newline at end of file
+# Momentum
+
+> *Definition 1*: the **momentum** $\mathbf{p}$ of a particle is defined as the product of the mass and velocity of the particle
+>
+> $$
+>   \mathbf{p} = m \mathbf{v},
+> $$
+>
+> with $m$ the mass of the particle and $\mathbf{v}$ the velocity of the particle.
+
+For the case that $\mathbf{v}: t \to \mathbf{v}(t) \implies \mathbf{v}'(t) = \mathbf{a}(t)$ we have the following theorem.
+
+> *Theorem 1*: let $\mathbf{v}$, $\mathbf{a}$ be the velocity and acceleration of a particle respectively, if we have 
+> 
+> $$
+>   \mathbf{v}: t \to \mathbf{v}(t) \implies \forall t \in \mathbb{R}: \mathbf{v}'(t) = \mathbf{a}(t),
+> $$ 
+>
+> then
+>
+> $$
+>   \mathbf{p}'(t) = \mathbf{F}(t),
+> $$
+>
+> for all $t \in \mathbb{R}$. 
+
+??? note "*Proof*:"
+
+    Will be added later.
+