Index: 4_appendix.html
===================================================================
--- 4_appendix.html	(revision 905)
+++ 4_appendix.html	(revision 906)
@@ -198,7 +198,7 @@
 and the naked hull.
 <p>
 <div class="img"><center>
-<p><img src="img/ex_sprial.png">
+<p><img src="img/ex_spiral.png">
 <p>Figure 4/8. Spiral can block the low level hull based algorithm.
 </center></div>
 <p>
Index: index.html
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--- index.html	(revision 905)
+++ index.html	(revision 906)
@@ -7,6 +7,6 @@
 <ul>
 	<li> 1. <a href="1_intro.html">Introduction</a>
 	<li> 2. <a href="2_topo.html">Detour search</a> (the topological aspect)
-	<li> 3. <a href="3_geo.html">Convex hull path</a> (geometric aspect)
+	<li> 3. <a href="3_hull.html">Convex hull path</a> (geometric aspect)
 	<li> 4. <a href="4_appendix.html">Appendix</a>
 </ul>