updated sources for unity

bib.bib

@@ -186,3 +186,31 @@
     url = {https://docs.unity3d.com/Manual/GridSnapping.html},
     year = {2020},
 }
+
+@inproceedings{Haas2014AHO,
+    title={A History of the Unity Game Engine},
+    author={John K Haas},
+    year={2014}
+}
+
+@misc{UNITY_DOWNLOADS,
+    title = {Unity herunterladen},
+    author = {Unity},
+    url = {https://unity3d.com/de/get-unity/download},
+    note = {letztter Zugriff am 7.2.2022},
+}
+
+@misc{UNITY_PRICING,
+    title = {Pläne und Preise},
+    url = {https://store.unity.com/de},
+    note = {letztter Zugriff am 7.2.2022},
+    author = {Unity},
+}
+
+@misc{WIKIPEDIA_2014,
+    title = {List of Unity games},
+    note = {lezter Zugriff am 7.2.2022},
+    author = {Wikipedia},
+    url = {https://en.wikipedia.org/wiki/List_of_Unity_games},
+    year = {2014},
+}