diff --git a/README b/README
index 4f7a879..cd86d95 100644
--- a/README
+++ b/README
@@ -173,3 +173,11 @@ Options:
 You may define the MCALL and INCLUDE environment variable prior to
 invoking macro11, as a path to directories containing macros or files to
 be included, respectively.
+
+=======================================================================
+
+Included in subdirectory obj2bin is a Perl script from Don North,
+copied from https://github.com/AK6DN/obj2bin. The copied version may
+get out of date; when in doubt check the original.
+
+=======================================================================