 		public function getChildIndex(child : ISceneNode) : int
 		{
 			if (child == null)
-				throw new Error("The 'child' parameter cannot be null.");
+				throw new Error('The 'child' parameter cannot be null.');
 			
 			for (var i : int = 0; i < _numChildren; i++)
 				if (_children[i] === child)

		public function addChildAt(node : ISceneNode, position : uint) : Group
		{
			if (!node)
				throw new Error("Parameter 'scene' must not be null.");

			node.parent = this;


		
		public function toString() : String
		{
			return '[' + getQualifiedClassName(this) + ' ' + name + ']';
		}

		/**
