diff --git a/Turbulence_Sim_v1_python/TurbSim_v1_main.py b/Turbulence_Sim_v1_python/TurbSim_v1_main.py
index 9518300..72862e0 100644
--- a/Turbulence_Sim_v1_python/TurbSim_v1_main.py
+++ b/Turbulence_Sim_v1_python/TurbSim_v1_main.py
@@ -1,6 +1,11 @@
 '''
 Collection of Optical Functions for Turbulence Simulator
 
+Nicholas Chimitt and Stanley H. Chan "Simulating anisoplanatic turbulence
+by sampling intermodal and spatially correlated Zernike coefficients," Optical Engineering 59(8), Aug. 2020
+
+ArXiv:  https://arxiv.org/abs/2004.11210
+
 Nicholas Chimitt and Stanley Chan
 Copyright 2021
 Purdue University, West Lafayette, In, USA.