11 files changed, 8 insertions, 15 deletions
diff --git a/source/know/concept/feynman-diagram/boson.avif b/source/know/concept/feynman-diagram/boson.avif
new file mode 100644
index 0000000..576e668
--- /dev/null
+++ b/source/know/concept/feynman-diagram/boson.avif
diff --git a/source/know/concept/feynman-diagram/interaction.png b/source/know/concept/feynman-diagram/boson.png
index 3c2d093..3c2d093 100644
--- a/source/know/concept/feynman-diagram/interaction.png
+++ b/source/know/concept/feynman-diagram/boson.png
diff --git a/source/know/concept/feynman-diagram/example.avif b/source/know/concept/feynman-diagram/example.avif
new file mode 100644
index 0000000..0dfa15c
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+++ b/source/know/concept/feynman-diagram/example.avif
diff --git a/source/know/concept/feynman-diagram/conservation.png b/source/know/concept/feynman-diagram/example.png
index 1d19fd0..1d19fd0 100644
--- a/source/know/concept/feynman-diagram/conservation.png
+++ b/source/know/concept/feynman-diagram/example.png
diff --git a/source/know/concept/feynman-diagram/fermion-heavy.avif b/source/know/concept/feynman-diagram/fermion-heavy.avif
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index 0000000..6618736
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+++ b/source/know/concept/feynman-diagram/fermion-heavy.avif
diff --git a/source/know/concept/feynman-diagram/fullgf.png b/source/know/concept/feynman-diagram/fermion-heavy.png
index f376ef2..f376ef2 100644
--- a/source/know/concept/feynman-diagram/fullgf.png
+++ b/source/know/concept/feynman-diagram/fermion-heavy.png
diff --git a/source/know/concept/feynman-diagram/fermion-light.avif b/source/know/concept/feynman-diagram/fermion-light.avif
new file mode 100644
index 0000000..196334b
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+++ b/source/know/concept/feynman-diagram/fermion-light.avif
diff --git a/source/know/concept/feynman-diagram/freegf.png b/source/know/concept/feynman-diagram/fermion-light.png
index 632ccaf..632ccaf 100644
--- a/source/know/concept/feynman-diagram/freegf.png
+++ b/source/know/concept/feynman-diagram/fermion-light.png
diff --git a/source/know/concept/feynman-diagram/impurity.avif b/source/know/concept/feynman-diagram/impurity.avif
new file mode 100644
index 0000000..1f78d10
--- /dev/null
+++ b/source/know/concept/feynman-diagram/impurity.avif
diff --git a/source/know/concept/feynman-diagram/perturbation.png b/source/know/concept/feynman-diagram/impurity.png
index 2e8fbf6..2e8fbf6 100644
--- a/source/know/concept/feynman-diagram/perturbation.png
+++ b/source/know/concept/feynman-diagram/impurity.png
diff --git a/source/know/concept/feynman-diagram/index.md b/source/know/concept/feynman-diagram/index.md
index c36e7df..ace8dbc 100644
--- a/source/know/concept/feynman-diagram/index.md
+++ b/source/know/concept/feynman-diagram/index.md
@@ -25,6 +25,7 @@ Below, we go through the most notable components of Feynman diagrams
 and how to translate them into a mathematical expression.
 
 
+
 ## Real space
 
 The most common component is a **fermion line**, which represents
@@ -37,9 +38,7 @@ Let the subscript $$I$$ refer to the
 and $$\mathcal{T}\{\}$$ denote the
 [time-ordered product](/know/concept/time-ordered-product/):
 
-<a href="freegf.png">
-<img src="freegf.png" style="width:60%">
-</a>
+{% include image.html file="fermion-light.png" width="60%" alt="Fermion line diagram" %}
 
 $$\begin{aligned}
     = i \hbar G_{s_2 s_1}^0(\vb{r}_2, t_2; \vb{r}_1, t_1)
@@ -59,9 +58,7 @@ Less common is a **heavy fermion line**, representing
 a causal Green's function $$G$$ for the entire Hamiltonian $$\hat{H}$$,
 where the subscript $$H$$ refers to the [Heisenberg picture](/know/concept/heisenberg-picture/):
 
-<a href="fullgf.png">
-<img src="fullgf.png" style="width:60%">
-</a>
+{% include image.html file="fermion-heavy.png" width="60%" alt="Heavy fermion line diagram" %}
 
 $$\begin{aligned}
     = i \hbar G_{s_2 s_1}(\vb{r}_2, t_2; \vb{r}_1, t_1)
@@ -75,9 +72,7 @@ which we assume to be instantaneous, i.e. time-independent
 hence it starts and ends at the same time,
 and no arrow is drawn:
 
-<a href="interaction.png">
-<img src="interaction.png" style="width:60%">
-</a>
+{% include image.html file="boson.png" width="60%" alt="Boson/interaction line diagram" %}
 
 $$\begin{aligned}
     = \frac{1}{i \hbar} W_{s_2 s_1}(\vb{r}_2, t_2; \vb{r}_1, t_1)
@@ -99,9 +94,7 @@ $$\begin{aligned}
 One-body (time-dependent) operators $$\hat{V}$$ in $$\hat{H}_1$$
 are instead represented by a special vertex:
 
-<a href="perturbation.png">
-<img src="perturbation.png" style="width:35%">
-</a>
+{% include image.html file="impurity.png" width="35%" alt="One-body perturbation (e.g. impurity) diagram" %}
 
 $$\begin{aligned}
     = \frac{1}{i \hbar} V_s(\vb{r}, t)
@@ -148,6 +141,7 @@ so that a particle with a given spin propagates
 from vertex to vertex without getting flipped.
 
 
+
 ## Fourier space
 
 If the system is time-independent and spatially uniform,
@@ -177,9 +171,7 @@ Working in Fourier space allows us to simplify calculations.
 Consider the following diagram and the resulting expression,
 where $$\tilde{\vb{r}} = (\vb{r}, t)$$, and $$\tilde{\vb{k}} = (\vb{k}, \omega)$$:
 
-<a href="conservation.png">
-<img src="conservation.png" style="width:40%">
-</a>
+{% include image.html file="example.png" width="40%" alt="Example: fermion-fermion interaction" %}
 
 $$\begin{aligned}
     &= (i \hbar)^3 \sum_{s s'} \!\!\iint \dd{\tilde{\vb{r}}} \dd{\tilde{\vb{r}}'}
@@ -274,6 +266,7 @@ then conservation removes all internal variables,
 so no integrals would be needed.
 
 
+
 ## Imaginary time
 
 Feynman diagrams are also useful when working with