diff --git a/README.md b/README.md
index bd41aac..44b24fd 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,8 @@ Usage:
 
 Files are combined in the order they are given. Output is optional (defaults to combined.pdf).
 
+Command line parsing code comes from this [seed program](https://github.com/cgarbin/seed-python/blob/master/seed-command-line-arg-parsing.py).
+
 ### Note
 
 This code is using a [workaround for PyPDF2](https://stackoverflow.com/a/49927541/336802) for the "empty output file wiht Python 3" issue documented [here](https://github.com/mstamy2/PyPDF2/issues/293).