diff --git a/km3buu/physics.py b/km3buu/physics.py
index b1e7e06aba4b24687482c52a13e04b009c1ab6f6..d7f18b25365ddd57d1b25d98e06584b8c55d13ea 100644
--- a/km3buu/physics.py
+++ b/km3buu/physics.py
@@ -2,6 +2,9 @@
 """
 Additional physics functionality
 
+Visible energy:
+* Implementation applied from JPP
+* Theory by M. Dentler https://inspirehep.net/literature/1321036
 """
 
 __author__ = "Johannes Schumann"