Add pdf file to 1987/heckbert

To prevent a possible 404 in the future the file
1987/heckbert/FoldSpindleMutilate.pdf was added as it is part of the
judges' remarks.

1987/heckbert/index.html

@@ -414,10 +414,10 @@ To compile on a 16 bit machine, change 300000 to 30000.</p>
 <p>Folding at the wrong length may be equivalent to a “Spindle or Mutilate” operation. For example:</p>
 <pre><code>    ./heckbert 40 &lt; heckbert.c &gt; ph.c ; make ph ; ./ph 20 &lt; heckbert.c &gt; bar.c ; make bar</code></pre>
 <p>Try not to
-<a href="https://repository.library.brown.edu/studio/item/bdr:788264/PDF/">Fold, Spindle or Mutilate</a>
+<a href="FoldSpindleMutilate.pdf">Fold, Spindle or Mutilate</a>
 files. :-)</p>
 <p>The judges used this program to fold up very long lines which the
-BSD fold(1) was unable to process. This program has been added to
+BSD <code>fold(1)</code> was unable to process. This program has been added to
 the contest tool chest.</p>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <p>No remarks were provided by the author.</p>
@@ -450,6 +450,7 @@ the contest tool chest.</p>
 <li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1987/heckbert/Makefile">Makefile</a> - entry Makefile</li>
 <li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1987/heckbert/heckbert.orig.c">heckbert.orig.c</a> - original source code</li>
 <li><a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1987/heckbert/try.sh">try.sh</a> - script to try entry</li>
+<li><a href="FoldSpindleMutilate.pdf">FoldSpindleMutilate.pdf</a> - cultural history of the punch card</li>
 </ul>
 <h2 id="secondary-files">Secondary files</h2>
 <ul>