diff --git a/Gemfile b/Gemfile
index 6bb9eb9..924f4eb 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,2 +1,4 @@
 gem 'github-pages'
 source 'https://rubygems.org'
+
+gem "webrick", "~> 1.7"
diff --git a/_config.yml b/_config.yml
index 489d9a3..1c3e6fc 100644
--- a/_config.yml
+++ b/_config.yml
@@ -13,7 +13,6 @@ author :
   name : Karl Broman
   email : kbroman@gmail.com
   github : kbroman
-  twitter : kwbroman
   feedburner : nil
 
 production_url : https://kbroman.github.io/github_tutorial
diff --git a/pages/resources.md b/pages/resources.md
index 7d05379..c600c2b 100644
--- a/pages/resources.md
+++ b/pages/resources.md
@@ -11,7 +11,7 @@ for learning to use [git](https://git-scm.com) and
 
 Here are some examples.
 
-- The [git documentation](https://git-scm.com/documentation)
+- The [git documentation](https://git-scm.com/docs)
 
 - The [Pro Git book](https://git-scm.com/book)
 
@@ -32,10 +32,10 @@ Here are some examples.
 - [Git and Github videos for beginners](https://www.dataschool.io/git-and-github-videos-for-beginners/)
   by [Kevin Markham](https://www.dataschool.io/about/)
 
-- Using GitHub with [RStudio](https://www.rstudio.com):
+- Using GitHub with [RStudio](https://posit.co/download/rstudio-desktop/):
 
-  - [Using GitHub with R and Rstudio](https://markrchristie.wordpress.com/2013/11/26/using-github-with-r-and-rstudio/)
-    by [Mark Christie](https://markrchristie.wordpress.com/)
+  - [Using GitHub with R and Rstudio](https://www.molecularecologist.com/2013/11/12/using-github-with-r-and-rstudio/)
+    by [Mark Christie](https://www.christielab.com/)
 
   - [Getting started with GitHub](https://jennybc.github.io/2014-05-12-ubc/ubc-r/session2.4_github.html)
     from materials for a
@@ -49,5 +49,3 @@ Here are some examples.
 - [Slides for lecture I gave about git/github, with notes](https://kbroman.org/Tools4RR/assets/lectures/04_git_withnotes.pdf)
 
 - [My brief summary of git commands](https://github.com/kbroman/Tools4RR/tree/master/04_Git/GitCommands/git_notes.md)
-
-