Index: R-exts.texi
===================================================================
--- R-exts.texi	(revision 58901)
+++ R-exts.texi	(working copy)
@@ -284,6 +284,11 @@
 would be good practice to avoid the shell metacharacters
 @code{()@{@}'[]$}.
 
+Source files should ideally include a succinct comment header to
+identify the author, copyright, and license terms. This has proved
+useful in catching errors where code was copied between packages that
+were meant to be distributed under different licenses.
+
 A source package if possible should not contain binary executable files:
 they are not portable, and a security risk if they are of the
 appropriate architecture.  @command{R CMD check} will warn about