add link to 9wm page
diff --git a/man/man1/rio.1 b/man/man1/rio.1
index 4e30e58..5d1f014 100644
--- a/man/man1/rio.1
+++ b/man/man1/rio.1
@@ -37,7 +37,7 @@
 policies of Plan 9's 
 .I rio
 window manager.
-Rio is derived from David Hogan's \*(85.
+Rio is derived from David Hogan's 9wm.
 .PP
 The
 .B \-grey
@@ -211,3 +211,11 @@
 .SH "SEE ALSO"
 .IR 9term (1),
 .IR xterm (1)
+.PP
+As mentioned above,
+.I rio
+is mainly maintenance updates
+applied to the original
+.I 9wm
+by David Hogan; see
+.HR http://unauthorised.org/dhog/9wm.html "" .