diff --git a/environment.yml b/environment.yml
index 40eb2503..55a26b67 100644
--- a/environment.yml
+++ b/environment.yml
@@ -6,12 +6,11 @@ dependencies:
   - anaconda=2020.07
   - pip
   - pip:
-    - git+https://github.com/executablebooks/jupyter-book.git
+    - jupyter-book
     - sphinxext-rediraffe
-    - git+https://github.com/executablebooks/sphinx-multitoc-numbering
-    - git+https://github.com/executablebooks/sphinx-exercise.git
+    - sphinx-multitoc-numbering
     - joblib
     - interpolation
-    - git+https://github.com/QuantEcon/sphinx-tojupyter.git
-    - git+https://github.com/QuantEcon/quantecon-book-theme.git
+    - sphinx-tojupyter
+    - quantecon-book-theme
 
diff --git a/lectures/_config.yml b/lectures/_config.yml
index 2c48ad48..ce878150 100644
--- a/lectures/_config.yml
+++ b/lectures/_config.yml
@@ -12,7 +12,7 @@ html:
   baseurl: https://python.quantecon.org/
 
 sphinx:
-  extra_extensions: [sphinx_multitoc_numbering, sphinx_exercise, sphinxext.rediraffe, sphinx_tojupyter]
+  extra_extensions: [sphinx_multitoc_numbering, sphinxext.rediraffe, sphinx_tojupyter]
   config:
     html_favicon: _static/lectures-favicon.ico
     html_theme: quantecon_book_theme