ref="#example-2-adding-two-signals" class="nav-link">Example 2: Adding two signals</a>
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            <li class="nav-item" data-level="3"><a href="#example-3-multiplying-two-signals" class="nav-link">Example 3: Multiplying two signals</a>
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            </li>
            <li class="nav-item" data-level="3"><a href="#example-4-parallel-composition" class="nav-link">Example