diff --git a/scripts/data_extraction.py b/scripts/data_extraction.py
index 66f57e1..cfced69 100755
--- a/scripts/data_extraction.py
+++ b/scripts/data_extraction.py
@@ -45,6 +45,12 @@ Created on Tue Aug  6 12:56:03 2019
 #5. chain
 #6. wild_pos
 #7. wild_chain_pos
+
+#-------------
+# requires
+#-------------
+#reference_dict.py
+#tidy_split.py
 #=======================================================================
 #%% load libraries
 import os, sys