link to mdn flex doc

diff --git a/docs/4.0/layout/grid.md b/docs/4.0/layout/grid.md
index 96f2beaf6ad7111e324b4235cd631b07e19f70ad..b61ecd3df43135d8014a1dbc8dfdf11a7e3d5bbc 100644 (file)
--- a/docs/4.0/layout/grid.md
+++ b/docs/4.0/layout/grid.md
@@ -8,7 +8,7 @@ toc: true
 
 ## How it works
 
-Bootstrap's grid system uses a series of containers, rows, and columns to layout and align content. It's built with flexbox and is fully responsive. Below is an example and an in-depth look at how the grid comes together.
+Bootstrap's grid system uses a series of containers, rows, and columns to layout and align content. It's built with [flexbox](https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_Flexible_Box_Layout/Using_CSS_flexible_boxes) and is fully responsive. Below is an example and an in-depth look at how the grid comes together.
 
 <div class="bd-example bd-example-row">
 <div class="container">