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@@ -1313,7 +1313,7 @@ <h3>Aren't Phase Modulation and Frequency Modulation equivalent? Why have both?<
         always equivalent. They are only identical when the modulator signal is a
         sinusoid, but with each added harmonic, PM and FM start to differ more and
         more. A detailed mathematical explanation of this is shown in
-        <a href="https://github.com/attilammagyar/js80p/blob/main/pm-fm-equivalence.md" target="_blank">here</a>.</p>
+        <a href="https://github.com/attilammagyar/js80p/blob/main/doc/pm-fm-equivalence.pdf" target="_blank">here</a>.</p>
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       <div class="section" id="faq-name">