Add a reference to dictnotes.txt.  It does no good if you don't know it's
there or where to find it.
diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 6c86235..f0e93f8 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -1,6 +1,12 @@
 
 /* Dictionary object implementation using a hash table */
 
+/* The distribution includes a separate file, Objects/dictnotes.txt,
+   describing explorations into dictionary design and optimization.  
+   It covers typical dictionary use patterns, the parameters for
+   tuning dictionaries, and several ideas for possible optimizations.
+*/
+
 #include "Python.h"
 
 typedef PyDictEntry dictentry;