diff --git a/documentation/ref-manual/ref-variables.xml b/documentation/ref-manual/ref-variables.xml
index ad87a63312..45015a4096 100644
--- a/documentation/ref-manual/ref-variables.xml
+++ b/documentation/ref-manual/ref-variables.xml
@@ -9589,6 +9589,15 @@ recipes-graphics/xorg-font/font-alias_1.0.3.bb:PR = "${INC_PR}.3"
      PREFERRED_VERSION_python = "2.7.3"
      PREFERRED_VERSION_linux-yocto = "3.19%"
                     </literallayout>
+                    If you want to force a particular version of a recipe,
+                    you can use "forcevariable" as follows:
+                    <literallayout class='monospaced'>
+     PREFERRED_VERSION_linux-yocto_forcevariable = "3.4%"
+                    </literallayout>
+                    Another method is to use a machine override:
+                    <literallayout class='monospaced'>
+     PREFERRED_VERSION_linux-yocto_qemux86 = "3.4%"
+                    </literallayout>
                 </para>
             </glossdef>
         </glossentry>