diff --git a/Internals.md b/Internals.md
index 6e6dbd2..3f196ed 100644
--- a/Internals.md
+++ b/Internals.md
@@ -4,3 +4,8 @@ MicroPython uses [string interning](http://en.wikipedia.org/wiki/String_internin
 
 MicroPython uses [Open addressing](http://en.wikipedia.org/wiki/Open_addressing) with [Linear probing](http://en.wikipedia.org/wiki/Linear_probing) of step = 1 for implementation of dictionaries. Rehashing happens when last free slot is used (on reaching loadfactor = 1.0).
 
+# CPython internals
+
+(For reference and comparison.)
+
+* [The structure of .pyc files](http://nedbatchelder.com/blog/200804/the_structure_of_pyc_files.html)