Add notebook link

Author: kschweikert

tracing.html

@@ -137,7 +137,7 @@ <h2 class="w3-border-bottom w3-border-light-grey w3-padding-16">What samples are
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-            <p> The full example with changable variables for location and industry (NAICS Code) to investigate is availabe: 
+            <p> The full example with changable variables for location and industry (NAICS Code) to investigate is availabe: <a href="https://colab.research.google.com/github/SAWGraph/public/blob/main/UseCases/UC3-Tracing/SAWGraph_Y3_Demo_TracingDownstream.ipynb">Tracing Downstream</a>
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             <h2 class="w3-border-bottom w3-border-light-grey w3-padding-16">What are the downstream fish tissue and surface water results below Converted Paper Manufacturing Facilities in Maine? </h2>
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