diff --git a/html/course.html b/html/course.html
index f6ec858..6f60fce 100644
--- a/html/course.html
+++ b/html/course.html
@@ -47,8 +47,14 @@ <h2>参考资料</h2>
                 </ol>
                 <h3>Turth table related</h3>
                 <ol class="custom-list">
-                    <li><a href="references/endianness.html">Endianness.</a></li>
-                    <li><a href="references/kitty_tt0.html">Show case in Kitty.</a> Truth table: Projection, Mask and Endianness.</li>
+                    <li><a
+                            href="references/endianness.html">Endianness.</a></li>
+                    <li><a href="references/kitty_tt0.html">Show case in
+                            Kitty.</a> Truth table: Projection, Mask and
+                        Endianness.</li>
+                    <li><a href="pdf/Kitty_Permutation.pdf">Show case in
+                            Kitty.</a> Truth table: Simple illustration of
+                        permutation technique.</li>
                 </ol>
             </section>
         </main>
diff --git a/html/pdf/Kitty_Permutation.pdf b/html/pdf/Kitty_Permutation.pdf
new file mode 100644
index 0000000..c4e5167
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