diff --git a/book/Introduction/Authors.md b/book/Introduction/Authors.md
index d1153c0..c209741 100644
--- a/book/Introduction/Authors.md
+++ b/book/Introduction/Authors.md
@@ -2,7 +2,7 @@
 
 ```{figure} ../Pedagogy/Figures/team.jpg
 ---
-width:70%
+width: 70%
 ---
 Part of the team discussing one of the potential demonstrations of the third edition of Show*de*Fysica.
 ```
diff --git a/book/Introduction/tableOC.md b/book/Introduction/tableOC.md
index b058272..da82ccf 100644
--- a/book/Introduction/tableOC.md
+++ b/book/Introduction/tableOC.md
@@ -9,7 +9,7 @@ align: right
 **Introduction**
 1. [About this book](../Introduction/About.ipynb)
 2. [Preface](../Introduction/Foreword.md)
-3. [Preface from the editor](../introduction/Preface2.md)
+3. [Preface from the editor](../Introduction/Preface2.md)
 4. [About the authors](../Introduction/Authors.md)
 5. [NVON](../Introduction/NVON.md)
 6. [Python](../Introduction/Python%20summary.ipynb)
diff --git a/book/Pedagogy/Argumentation.ipynb b/book/Pedagogy/Argumentation.ipynb
index 31e25e1..015cacf 100644
--- a/book/Pedagogy/Argumentation.ipynb
+++ b/book/Pedagogy/Argumentation.ipynb
@@ -17,7 +17,7 @@
     "\n",
     "```{figure} Figures/sdf.jpg\n",
     "---\n",
-    "width=70%\n",
+    "width: 70%\n",
     "---\n",
     "The [signing rod](../demos/demo81/demo81.ipynb), how many measurements do we need before we have a 'convincing' value for Young's modulus for a specific material?\n",
     "```\n",
diff --git a/book/Pedagogy/Introduction.md b/book/Pedagogy/Introduction.md
index 88be65f..942d587 100644
--- a/book/Pedagogy/Introduction.md
+++ b/book/Pedagogy/Introduction.md
@@ -58,7 +58,7 @@ width: 75%
 [Determination of $g$](../demos/demo73/demo73.ipynb) revolves around the question how you can determine the acceleration due to gravity as precise as possible.
 ```
 
-Our [demonstrations on teaching scientific inquiry](../demos/Inquirydemos.md) cover this learning objective. These demonstrations aim at teaching students to become aware of the decisions they have to make when conceiving a scientific investigation. They are meant to teach students to thoroughly consider various options and determine, also in regard of the practical limitations, what decision is 'best' from a scientific perspective. [Argumentation](./Argumentation.md) plays a major role in this. 
+Our [demonstrations on teaching scientific inquiry](../demos/Inquirydemos.md) cover this learning objective. These demonstrations aim at teaching students to become aware of the decisions they have to make when conceiving a scientific investigation. They are meant to teach students to thoroughly consider various options and determine, also in regard of the practical limitations, what decision is 'best' from a scientific perspective. [Argumentation](./Argumentation.ipynb) plays a major role in this. 
 
 Teaching students how to investigate their world independently in a scientific way includes addressing questions such as:
 1. What does it mean when some claim is said to be *"scientifically proven"*? 
@@ -92,7 +92,7 @@ In physics research, all of these questions matter but in demonstrations this is
 
 Questions like question 1. encourage [thinking-back-and-forth between theory and practice](../Pedagogy/BackAndForthThinking.md). In demonstrations of this kind something often happens that your audience doesn't expect and that raises questions. This will allow you to illustrate how in physical research you are constantly testing theory and practice against each other. Students experience this with the support of the teacher in the demonstrations. 
 
-Questions like question 2. focus on [argumentation](../Pedagogy/Argumentation.md). When doing scientific inquiry students often seem satisfied with any answer they can find, without spending further effort in finding the most *convincing* answer available. In science only that optimally convincing answer would be good enough.
+Questions like question 2. focus on [argumentation](../Pedagogy/Argumentation.ipynb). When doing scientific inquiry students often seem satisfied with any answer they can find, without spending further effort in finding the most *convincing* answer available. In science only that optimally convincing answer would be good enough.
 But what do we find convincing in science, and why? Demonstrations can develop scientific understandings of this kind in students. 
 
 Questions such as question 3. deal with the [nature of science](../Pedagogy/Nos.md). In successful research the researcher is looking for something that was not yet known. 
diff --git a/book/_config.yml b/book/_config.yml
index 1640892..b7c2685 100644
--- a/book/_config.yml
+++ b/book/_config.yml
@@ -43,15 +43,19 @@ sphinx:
       use_thebe_lite: true
       exclude_patterns: ["**/**"]
     html_theme_options:
-      repository_url: https://github.com/TeachBooks/Showing-Physics #"https://gitlab.tudelft.nl/fpols/showing-physics"  # Online location of your book
+      repository_url:         https://github.com/TeachBooks/Showing-Physics #"https://gitlab.tudelft.nl/fpols/showing-physics"  # Online location of your book
       # path_to_book:  # Optional path to your book, relative to the repository root
       # branch:   # Which branch of the repository should be used when creating links (optional)
       use_repository_button: true
       use_issues_button: true
-      use_multitoc_numbering: true
+      # use_multitoc_numbering: true
       launch_buttons:
         thebe: true
+    html:
+      use_multitoc_numbering: true
     nb_render_text: ["remove-input", "hide-input"]  # to hide or remove input cells with tags
+    suppress_warnings: ['ref.duplicate'] # suppress warnings for duplicate labels
+    
   extra_extensions:
     - sphinx_exercise
     #- extensions.fa_extension # for fontawesome icons needed when converting to pdf
diff --git a/book/demos/demo43/demo43.md b/book/demos/demo43/demo43.md
index 9f3ab67..62d92ce 100644
--- a/book/demos/demo43/demo43.md
+++ b/book/demos/demo43/demo43.md
@@ -17,6 +17,7 @@
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Concepts:</td>
         <td style="text-align: left; padding: 3px; border: none; color: var(--text-color)">Force, motion, Newton's laws</td>
     </tr>
+</table>
 
 ## Introduction
 How can you experience force and motion in person without too much interference from that annoying, always present friction? With a bowling ball! During this demonstration in the hallway or gymnasium, some students try to influence the direction of a bowling ball with brooms and feel the essence of Newton's first and second law.
@@ -67,14 +68,15 @@ There is room for discussion here. Let students try it first. Then the question
 **10. Checking students' understanding**<br>
 Memphis is standing 10 meters in front of the center of an open goal. He receives a hard cross from Bergwijn's left and hits it exactly at right angles, perpendicular to the direction of travel. Explain with a drawing and reasoning why the ball might not go into the goal.
 
-
+<!-- 
 ```{figure} demo43_figure1.png
 ---
 width: 50%
 align: center
 ---
 some caption
-```
+``` 
+-->
 
 ## Physics background
 Newton's first and second laws are key here: The heavy bowling ball continues straight at a constant speed unless a net force is applied. With the broom you can change both the size and direction and speed of the ball.
\ No newline at end of file
diff --git a/book/references.bib b/book/references.bib
index 61f1587..13e34e7 100644
--- a/book/references.bib
+++ b/book/references.bib
@@ -30,7 +30,8 @@ @article{crouch2004classroom
   number={6},
   pages={835--838},
   year={2004},
-  publisher={American Association of Physics Teachers}
+  publisher={American Association of Physics Teachers},
+  doi = {10.1119/1.1707018}
 }
 
 @article{hidden2012,
@@ -41,7 +42,8 @@ @article{hidden2012
   number={2},
   pages={103--104},
   year={2012},
-  publisher={AIP Publishing}
+  publisher={AIP Publishing},
+  doi = {10.1119/1.3677286}
 }
 
 @article{demircioglu2019,
@@ -52,7 +54,8 @@ @article{demircioglu2019
   number={5},
   pages={055010},
   year={2019},
-  publisher={IOP Publishing}
+  publisher={IOP Publishing},
+  doi = {10.1088/1361-6552/ab2924}
 }
 
 @article{dekkers1998,
@@ -96,7 +99,8 @@ @article{pols2022defining
   number={1},
   pages={010111},
   year={2022},
-  publisher={APS}
+  publisher={APS},
+  doi = {10.1103/physrevphyseducres.18.010111 }
 }
 
 @article{mccomas2020principal,
@@ -105,7 +109,8 @@ @article{mccomas2020principal
   journal={Nature of science in science instruction: Rationales and strategies},
   pages={35--65},
   year={2020},
-  publisher={Springer}
+  publisher={Springer},
+  doi = {10.1007/978-3-030-57239-6_3}
 }
 
 @book{white2014probing,
@@ -165,7 +170,8 @@ @article{spaan2022analysing
   journal={Research in Science \& Technological Education},
   pages={1--18},
   year={2022},
-  publisher={Taylor \& Francis}
+  publisher={Taylor \& Francis},
+  doi = {10.1080/02635143.2022.2098265 }
 }
 
 @article{barretto2022physical,
@@ -176,7 +182,8 @@ @article{barretto2022physical
   number={5},
   pages={053003},
   year={2022},
-  publisher={IOP Publishing}
+  publisher={IOP Publishing},
+  doi={10.1088/1361-6552/ac7cb2}
 }
 
 @misc{SCHLICHTING, 
@@ -248,7 +255,8 @@ @article{hodson2014learning
   number={15},
   pages={2534--2553},
   year={2014},
-  publisher={Taylor \& Francis}
+  publisher={Taylor \& Francis},
+  doi = {10.1080/09500693.2014.899722 }  
 }
 
 @article{dekkers1999drogen,
@@ -433,7 +441,8 @@ @article{kok2021acoustic
   number={3},
   pages={181--184},
   year={2021},
-  publisher={AIP Publishing}
+  publisher={AIP Publishing},
+  doi={10.1119/10.0003659}
 }
 
 @article{Braun2011,
@@ -442,7 +451,8 @@ @article{Braun2011
   title = {How Rosalind Franklin Discovered the Helical Structure of DNA: Experiments in Diffraction},
   journal = {The Physics Teacher},
   volume = {49},
-  pages = {140}
+  pages = {140},
+  doi = {10.1119/1.3555496}
   }
 
   @article{cross2023comment,
@@ -453,7 +463,8 @@ @article{cross2023comment
   number={6},
   pages={425--426},
   year={2023},
-  publisher={American Association of Physics Teachers}
+  publisher={American Association of Physics Teachers},
+  doi={10.1119/5.0148218 }
 }
 
 @article{schmidt2024experimental,
@@ -464,7 +475,8 @@ @article{schmidt2024experimental
   number={5},
   pages={346--349},
   year={2024},
-  publisher={AIP Publishing}
+  publisher={AIP Publishing},
+  doi={10.1119/5.0159623}
 }
 
 @article{mungan2023pulling,
@@ -475,7 +487,8 @@ @article{mungan2023pulling
   number={3},
   pages={178--181},
   year={2023},
-  publisher={AIP Publishing}
+  publisher={AIP Publishing},
+  doi={10.1119/5.0042450}
 }
 
 @article{mooldijk2005,
@@ -505,7 +518,8 @@ @article{pols2022would
   number={9},
   pages={1481--1505},
   year={2022},
-  publisher={Taylor \& Francis}
+  publisher={Taylor \& Francis},
+  doi = {10.1080/09500693.2022.2083251},
 }
 
 @phdthesis{pols2023development,
@@ -543,7 +557,8 @@ @article{pols2021s
   number={4},
   pages={045004},
   year={2021},
-  publisher={IOP Publishing}
+  publisher={IOP Publishing},
+  doi={10.1088/1361-6552/abf208}
 }
 
 @article{stadermann2021don,
@@ -554,7 +569,8 @@ @article{stadermann2021don
   number={2},
   pages={025014},
   year={2021},
-  publisher={IOP Publishing}
+  publisher={IOP Publishing},
+  doi={10.1088/1361-6552/ac39e7}
 }
 
 @proceedings{kempa1988functions,