diff --git a/intro.Rmd b/intro.Rmd
index 85bad7a..bf19e52 100644
--- a/intro.Rmd
+++ b/intro.Rmd
@@ -231,8 +231,8 @@ This book isn't just the product of Hadley and Garrett, but is the result of man
   learning perspective, and the difference between hypothesis generation and 
   hypothesis confirmation.
 
-* Yihui Xie for his work on the bookdown package, and for tirelessly 
-  responding to my feature requests.
+* Yihui Xie for his work on the [bookdown](https://github.com/rstudio/bookdown) 
+  package, and for tirelessly responding to my feature requests.
 
 * Bill Behrman for his thoughtful reading of the entinre book, and for trying 
   it out with his data science class at Stanford.
@@ -256,7 +256,7 @@ cat(".\n")
 
 ## Colophon
 
-An online version of this book is available at <http://r4ds.had.co.nz>. It will continue to evolve in between reprints of the physical book. The source of the book is available at <http://github.com/hadley/r4ds>. The book is powered by <https://bookdown.org> which makes it easy to turn R markdown files into html, pdf, and epub.
+An online version of this book is available at <http://r4ds.had.co.nz>. It will continue to evolve in between reprints of the physical book. The source of the book is available at <https://github.com/hadley/r4ds>. The book is powered by <https://bookdown.org> which makes it easy to turn R markdown files into html, pdf, and epub.
 
 This book was built with: