Physics_EG.md

@@ -3,3 +3,5 @@ Electron Photon Interactions and Cascades
 [OrangeBible.pdf](uploads/f39dbfc647ad25c6b3c6eac61ebcac0e/OrangeBible.pdf)
 
 [Tsai PAIR PRODUCTION AND BREMSSTRAHLUNG OF CHARGED LEPTONS pdf](https://inspirehep.net/files/be2ffc45ed59b1b28208cc386c1e16b3)
+
+[PROPOSAL: A library to propagate leptons and high energy photons](doi.org/10.1088/1742-6596/1690/1/012021)
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