diff --git a/README.md b/README.md
index 83923141..8ea2b427 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,8 @@
 
 ## Introduction
 
+OpenSCAD uses three library locations, the installation library, built-in library, and user defined libraries. It's convenient to set `OPENSCADPATH`. Check [Setting OPENSCADPATH](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Libraries#Setting_OPENSCADPATH) in [OpenSCAD User Manual/Libraries](https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Libraries) for details.
+
 Every module or function is located in the file which has the same name as the module or the function. For example, if you want to use the `line2d` module to draw a line, `include <line2d.scad>;` first. 
 
 	include <line2d.scad>;