Add sources (#69)

This adds more sources to some places where I didn't add them before.

book/basics/how-sourdough-works.tex

@@ -183,7 +183,7 @@ seeds, requiring water to enter quickly. Yet the seed must also defend itself
 against animals and potentially hazardous bacteria and fungi, requiring some
 barrier to protect the embryo inside. A way for the plant to achieve both goals
 would be for most of the enzymes to exist in the outer parts of the hull. As a
-result, they are activated first (source needed). Therefore, by just adding a
+result, they are activated first \cite{enzymatic+activity+whole+wheat}. Therefore, by just adding a
 little bit of whole flour to your dough, you should be able to significantly
 improve the enzymatic activity of your dough. That's why, for plain white flour
 doughs, I usually add 10\textendash20\% whole-wheat flour.

book/history/sourdough-history.tex

@@ -42,7 +42,7 @@ By feeding your sourdough starter, you are selectively breeding
 microorganisms that are good at eating your flour. With
 each iteration, your sourdough knows how to better ferment the flour
 at hand. This is also the reason why more mature sourdough starters sometimes
-tend to leaven doughs faster (source needed). It is crazy if you
+tend to leaven doughs faster \cite{review+of+sourdough+starters}. It is crazy if you
 think about it. People have been using this process despite not
 knowing what was actually going on for thousands of years! The
 sourdough in itself is a symbiotic relationship. But the sourdough

book/references.bib

@@ -211,7 +211,7 @@
   note         = {Accessed: 2022-06-23}
 }
 
-@article{effects+temperature+flavor,
+@article{effects+temperature+flavor+wine,
   title        = {Effects of Fermentation Temperature on Key Aroma Compounds and Sensory Properties of Apple Wine},
   author       = {Bangzhu Peng et al.},
   year         = {2015},
@@ -333,3 +333,28 @@
 	url = {https://en.wikipedia.org/wiki/Whole_grain#/media/File:Wheat-kernel_nutrition.svg},
   note = {Accessed: 2023-03-30}
 }
+
+@article{enzymatic+activity+whole+wheat,
+	author = {Rachana Poudel},
+	title = {Enzymatic Activities and Compostional Properties of Whole Wheat Flour},
+  year = {2018},
+  page = {67},
+}
+
+@article{review+of+sourdough+starters,
+	author = {Calvert MD, Madden AA et al.},
+  title = {A review of sourdough starters: ecology, practices, and sensory quality with applications for baking and recommendations for future research},
+  year = {2021},
+  page = {3},
+	url = {https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8117929/#ref-36},
+  note = {Accessed: 2023-03-30}
+}
+
+@article{gluten+development+temperatures,
+	author = {Koga S., Böcker U. et al.},
+  title = {Influence of temperature during grain filling on gluten viscoelastic properties and gluten protein composition.},
+  year = {2015},
+  journal = {Journal of the Science of Food and Agriculture},
+	number = {96},
+	pages = {122-130}
+}

book/sourdough-starter/sourdough-starter-types.tex

@@ -201,7 +201,7 @@ In the stiffer environment the yeast thrives more. This means you will have
 more \ch{CO2} production and less acid production. In my tests this is a game
 changer especially if you are using weaker gluten flours. The wheat flours in
 my home country of Germany tend to be lower in gluten. For wheat to build gluten, warm conditions
-are preferred (SOURCE NEEDED). When following recipes from other bakers, I
+are preferred \cite{gluten+development+temperatures}. When following recipes from other bakers, I
 could never achieve similar results. When following timings my doughs would
 simply collapse and become super sticky. Only when I started to buy more
 expensive wheat flour did my results start to change. As not everyone can afford

book/troubleshooting/misc.tex

@@ -134,9 +134,9 @@ to use a flour that contains at least 12 percent protein.
 Generally the more protein the longer you can ferment your dough.
 
 Another option to achieve a more sour flavor could be to
-use a starter that produces more acetic acid. Acetic acid
-bacteria tend to be more common in rye starters (source needed).
-Chemically the acetic acid isn't as sour, but when tasting
+use a starter that produces more acetic acid. Based on my own
+experience, most of my pure rye starters produced stronger acetic
+notes. Chemically the acetic acid isn't as sour, but when tasting
 it will seem more sour. Make sure to use a starter that is at
 a hydration of around 100 percent. Acetic acid production
 requires oxygen. A too liquid starter tends to favor lactic