From 1c65b3c7d04ab7123bbc7fc9e420c8bd484927a1 Mon Sep 17 00:00:00 2001
From: Richard Kreckel <kreckel@ginac.de>
Date: Mon, 18 Apr 2016 22:18:20 +0200
Subject: [PATCH] Update reference to Robert C. Martin's "Acyclic Visitor"
 paper.

The source at objectmentor.com has been unavailble for a long while.
---
 ginac/basic.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/ginac/basic.h b/ginac/basic.h
index 3ae3282c..1af6f858 100644
--- a/ginac/basic.h
+++ b/ginac/basic.h
@@ -92,7 +92,8 @@ struct map_function {
 
 /** Degenerate base class for visitors. basic and derivative classes
  *  support Robert C. Martin's Acyclic Visitor pattern (cf.
- *  http://objectmentor.com/publications/acv.pdf). */
+ *  http://condor.depaul.edu/dmumaugh/OOT/Design-Principles/acv.pdf
+ *  or chapter 10 of Andrei Alexandrescu's "Modern C++ Design"). */
 class visitor {
 protected:
 	virtual ~visitor() {}
-- 
2.44.0