COPYING: Specify origin of the library
diff --git a/COPYING b/COPYING
index 22ac7b9..faefd8f 100644
--- a/COPYING
+++ b/COPYING
@@ -22,3 +22,9 @@
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 DEALINGS IN THE SOFTWARE.
+
+---
+
+The above is the version of the MIT "Expat" License used by X.org:
+
+    http://cgit.freedesktop.org/xorg/xserver/tree/COPYING