Copyright for 1992 added
diff --git a/Include/listobject.h b/Include/listobject.h
index cc1921d..710db2d 100644
--- a/Include/listobject.h
+++ b/Include/listobject.h
@@ -1,5 +1,5 @@
 /***********************************************************
-Copyright 1991 by Stichting Mathematisch Centrum, Amsterdam, The
+Copyright 1991, 1992 by Stichting Mathematisch Centrum, Amsterdam, The
 Netherlands.
 
                         All Rights Reserved