diff --git a/pandas_eval.py b/pandas_eval.py
index 81785a5..73524c3 100644
--- a/pandas_eval.py
+++ b/pandas_eval.py
@@ -3,8 +3,15 @@ import numpy as np
 import math
 import matplotlib.pyplot as plt
 
+# Stock Investors Financial Math
 # https://www.fmlabs.com/reference/default.htm?url=SimpleMA.htm
 
+# Alpha Vantage
+# https://www.alphavantage.co/documentation/
+
+# Pandas
+# https://pandas.pydata.org/pandas-docs/stable/index.html
+
 def sin(f, a, N):
 	result = np.empty(0)
 	for n in range(0, N):