bug fix

app.py

@@ -162,7 +162,7 @@ def main():
     st.pyplot(fig)
     
     st.markdown(body = """
-        **Sources:** [Bryan Lim et al. in Temporal Fusion Transformers (TFT) for Interpretable Multi-horizon Time Series Forecasting (https://duckduckgo.com). <br>
+        **Sources:** [Bryan Lim et al. in Temporal Fusion Transformers (TFT)](https://arxiv.org/abs/1912.09363). <br>
         **Demo created by:** [leuschnm](https://github.com/MalteLeuschner)
     """, unsafe_allow_html = True)