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diff --git a/system/knowledge/knowledge_messages.base.111.png b/system/knowledge/knowledge_messages.base.111.png
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diff --git a/system/knowledge/knowledge_monsters.base.111.png b/system/knowledge/knowledge_monsters.base.111.png
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diff --git a/system/knowledge/knowledge_recipes.base.111.png b/system/knowledge/knowledge_recipes.base.111.png
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diff --git a/system/knowledge/licence.txt b/system/knowledge/licence.txt
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--- /dev/null
+++ b/system/knowledge/licence.txt
@@ -0,0 +1,11 @@
+Licence for those pictures:
+
+- knowledge_generic.base.111.png is from http://commons.wikimedia.org/w/index.php?title=File:HREpolitics.svg&oldid=58248760 by Masterdeis and under CC-BY-SA 3.0
+
+- knowledge_gods.base.111.png is the copy of holy_symbol.clsc.111.png and under GPL 2
+
+- knowledge_messages.base.111.png is a reduction of http://commons.wikimedia.org/w/index.php?title=File:Temple_Scroll.png&oldid=65512408 which is in the public domain
+
+- knowledge_monsters.base.111.png is a rendering at 32x32 of http://commons.wikimedia.org/w/index.php?title=File:Dragon.svg&oldid=65944895 by Angelus under a CC-BY-SA 3.0 or GFDL 1.2 licence
+
+- knowledge_recipes.base.111 is a slight modification (adding a transparent background) and reduction of http://www.nasa.gov/mission_pages/hubble/science/hst_img_20080520.html which is from NASA and public domain since no copyright according to http://www.jsc.nasa.gov/policies.html#Guidelines