diff --git a/book/demos/demo04/demo04.md b/book/demos/demo04/demo04.md
index 47691af..bc54afe 100644
--- a/book/demos/demo04/demo04.md
+++ b/book/demos/demo04/demo04.md
@@ -97,7 +97,7 @@ width: 50%
align: center
name: demo04_fig4
---
-The market hall in Rotterdam is stacked according to the principle above. Figure obtained from: https://commons.wikimedia.org/wiki/File:Markthal-Rotterdam.jpg
+The market hall in Rotterdam is stacked according to the principle above. Figure obtained from: https://commons.wikimedia.org/wiki/File:Markthal-Rotterdam.jpg (CC BY-SA)
````
```
diff --git a/book/demos/demo28/demo28.md b/book/demos/demo28/demo28.md
index 63d164b..fa700d9 100644
--- a/book/demos/demo28/demo28.md
+++ b/book/demos/demo28/demo28.md
@@ -46,7 +46,7 @@ name: demo28_figure4
width: 50%
align: center
---
-Gulfstream, figure obtained from https://www.flickr.com/photos/gridarendal/31551868273
+Gulfstream, figure obtained from https://www.flickr.com/photos/gridarendal/31551868273 (CC BY-NC-SA 2.0)
```
## Equipment
diff --git a/book/demos/demo57/demo57.md b/book/demos/demo57/demo57.md
index 5534347..75f7ad3 100644
--- a/book/demos/demo57/demo57.md
+++ b/book/demos/demo57/demo57.md
@@ -71,7 +71,9 @@ width: 100%
align: center
name: demo57_fig2
---
-Left: The water jet bends towards the convex surface. Right: A ping pong ball is pulled into the water jet.
+The Coandă effect explained using a wat jet.\
+*Left:* The water jet bends towards the convex surface.\
+*Right:* A ping pong ball is pulled into the water jet.
```
The rolled-up A4 paper tube rolls down the plank. It leaves the plank with both velocity and rotation. Because of its speed, the cylinder experiences a kind of counter-wind, just like a cyclist feels the wind in their face when riding fast. The air flowing past is deflected more on the side of the paper cylinder that rotates with the air than on the other side. The air experiences an upward force, and the cylinder experiences an equal and opposite force downward. The cylinder experiences a force perpendicular to the axis of rotation downward. See {numref}`Figure {number}`. The ball rolling down the slope also experiences this force. However, in comparison to the gravitational force on the rolling object, this force is too small to significantly alter its trajectory.
diff --git a/book/demos/demo57/demo57_figures5.png b/book/demos/demo57/demo57_figures5.png
index a20ad95..85f70e0 100644
Binary files a/book/demos/demo57/demo57_figures5.png and b/book/demos/demo57/demo57_figures5.png differ
diff --git a/book/demos/demo60/demo60.md b/book/demos/demo60/demo60.md
index e9d8acb..2d5400e 100644
--- a/book/demos/demo60/demo60.md
+++ b/book/demos/demo60/demo60.md
@@ -1,9 +1,3 @@
-```{figure} ../../figures/checked.png
----
-width: 35%
-align: right
-```
-
# Flamecooler
@@ -17,7 +11,7 @@ align: right
Age group:
-
from grade 8, extension availabe for grade 11 and above
+
from grade 8, extension available for grade 11 and above
@@ -41,11 +35,9 @@ A burning candle is an everyday phenomenon, but the physical and chemical effect
width: 100%
align: center
---
-The visible flame of a candle disappears near a copper spiral.\
-_Photos by Aike Stortelder._
+The visible flame of a candle disappears near a copper spiral.
```
-
## Materials Needed
- Approximately 20 cm long, thick (Ø 1 to 2 mm) uninsulated copper wire
- Candle
@@ -58,7 +50,7 @@ Make a 1-2 cm long spiral from the copper wire by wrapping it around a pencil. T
Depending on the candle and the spiral, the experiment will be slightly different for everyone. Proper observation is therefore important.
1. Light the candle.
2. Slowly bring the spiral from above over the candle flame. Do not touch the wick with the spiral.
- - *Write down what you observe as precisely as possible. What surprises you?*
+ - *Write down what you observe as precisely as possible. What surprises you?*
- The visible flame will disappear at the spiral. If the spiral is loosely wound, you will still see a thin yellow flame in the center and a blue one around it. In other cases, the flame will go out. If smoke still rises, you can relight the flame above the spiral.
4. Alone or in pairs, explain what you see. Write down your hypothesis.
5. Collect the answers and ask for a substantiation of their hypotheses. This way, students learn to make connections between physical concepts and their own experiences. Do not reject any explanation.
@@ -85,7 +77,6 @@ align: center
Figure 2a. Temperature measured in (a) the invisible part and (b) the visible part of the flame.
```
-
## References
```{bibliography}
:filter: docname in docnames
diff --git a/book/demos/demo80/demo80.md b/book/demos/demo80/demo80.md
index 0bc80cd..2852243 100644
--- a/book/demos/demo80/demo80.md
+++ b/book/demos/demo80/demo80.md
@@ -56,7 +56,7 @@ width: 90%
align: center
name: demo80BBD
---
-Black body spectrum, figure taken from https://commons.wikimedia.org/wiki/File:BlackbodySpectrum_loglog_en.svg
+Black body spectrum, figure taken from https://commons.wikimedia.org/wiki/File:BlackbodySpectrum_loglog_en.svg (public domain).
```
## Physics background
diff --git a/book/demos/demo87/demo87.md b/book/demos/demo87/demo87.md
index 124130c..2381e7a 100644
--- a/book/demos/demo87/demo87.md
+++ b/book/demos/demo87/demo87.md
@@ -29,7 +29,7 @@ width: 70%
align: center
name: demo87_fig1
---
-The green laser beam appears to turn orange in olive oil. (Photo: Rutger Ockhorst.)
+The green laser beam appears to turn orange in olive oil.
```
## Equipment