diff --git a/research-notes b/research-notes
index da69921..52263c1 100644
--- a/research-notes
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@@ -1,2 +1,8 @@
 Info on windows (transmittance, U-factor, etc.)
     https://www.commercialwindows.org/vt.php
+    
+ Solar radiation values definition/relations
+    https://www.ammonit.com/en/wind-solar-wissen/solarmessung
+
+Computing DNI/DHI from GHI and solar position: 
+    https://plantpredict.com/algorithm/irradiance-radiation/