diff --git a/_config.yml b/_config.yml
index 7bc78dc..d836eb7 100644
--- a/_config.yml
+++ b/_config.yml
@@ -247,7 +247,7 @@ links:
       demo01: "• [Demo](https://data8.datahub.berkeley.edu/hub/user-redirect/git-pull?repo=https://github.com/data-8/materials-sp25&urlpath=tree/materials-sp25/lec/lec01/lec01.ipynb&branch=main)"
       demo02: ""
       demo03: "• [Demo](https://data8.datahub.berkeley.edu/hub/user-redirect/git-pull?repo=https://github.com/data-8/materials-sp25&urlpath=tree/materials-sp25/lec/lec03/lec03.ipynb&branch=main)"
-      demo04: ""
+      demo04: "• [Demo](https://data8.datahub.berkeley.edu/hub/user-redirect/git-pull?repo=https://github.com/data-8/materials-sp25&urlpath=tree/materials-sp25/lec/lec04/lec04.ipynb&branch=main)"
       demo05: ""
       demo06: ""
       demo07: ""
@@ -291,7 +291,7 @@ links:
       slide01: "[Slides](https://docs.google.com/presentation/d/1Rg3tyM3b68n8Ko5OzsnnvXSbeP-HARD5WlLKUfXXCFk/edit?usp=sharing)" 
       slide02: "[Slides](https://docs.google.com/presentation/d/1mpRbyc3oeT1vUFUs3zMztGVAjAGC7Gv9nweH3n8Zkz0/edit?usp=sharing)"
       slide03: "[Slides](https://docs.google.com/presentation/d/1k3YSZn0Cuxh_kD_iYj5i_pTPgIm2GZe4ysVlQvOHJzU/edit?usp=sharing)"
-      slide04: ""
+      slide04: "[Slides](https://docs.google.com/presentation/d/12danL6fLoxZy6BN43a349LxAHS6k8g5KzBYXM_If1aA/edit?usp=sharing)"
       slide05: ""
       slide06: ""
       slide07: ""