Added link to quaternion.

src/docs/asciidoc/jme3/rotate.adoc

@@ -11,7 +11,7 @@ _Bad news: 3D rotation is done using matrix calculus. +
 Good news: If you do not understand calculus, there are two simple rules how you get it right._
 
 
-*3D rotation* is a crazy mathematical operation where you need to multiply all vertices in your object by four floating point numbers; the multiplication is referred to as concatenation, the array of four numbers {x,y,z,w} is referred to as quaternion. Don't worry, the 3D engine does the tough work for you. All you need to know is:
+*3D rotation* is a crazy mathematical operation where you need to multiply all vertices in your object by four floating point numbers; the multiplication is referred to as concatenation, the array of four numbers {x,y,z,w} is referred to as <<jme3/quaternion#,quaternion>>. Don't worry, the 3D engine does the tough work for you. All you need to know is:
 
 *The Quaternion* is an object capable of deep-freezing and storing a rotation that you can apply to a 3D object.