      *  to the appropriate value.
      *
      *  <p>If <code>viewport</code> is null, 
-     *  change the vertical scroll position for line up or line down by calling 
+     *  calling this method changes the vertical scroll position for 
+     *  a line up or line down operation by calling 
      *  the <code>changeValueByStep()</code> method.</p>
      *
      *  @param increase Whether the line scoll is up (<code>true</code>) or
      *  down (<code>false</code>). 
      * 
-     *  @see mx.components.baseClasses.TrackBase#changeValueByStep()
-     *  @see mx.components.baseClasses.TrackBase#setValue()
+     *  @see spark.components.supportClasses.Range#changeValueByStep()
+     *  @see spark.components.supportClasses.Range#setValue()
      *  @see spark.core.IViewport
      *  @see spark.core.IViewport#verticalScrollPosition
      *  @see spark.core.IViewport#getVerticalScrollPositionDelta()

     *  to the appropriate value.
     *
     *  <p>If <code>viewport</code> is null, 
     *  change the vertical scroll position for page up or page down by calling 
     *  the <code>changeValueByPage()</code> method.</p>
     *
     *  @param increase Whether the page scroll is up (<code>true</code>) or
     *  down (<code>false</code>). 
     * 
     *  @see mx.components.baseClasses.TrackBase#changeValueByPage()
     *  @see mx.components.baseClasses.TrackBase#setValue()
     *  @see spark.core.IViewport
     *  @see spark.core.IViewport#verticalScrollPosition
     *  @see spark.core.IViewport#getVerticalScrollPositionDelta()     

        
    /**
     *  If <code>viewport</code> is not null, 
     *  changes the vertical scroll position for a page up or page down operation 
     *  by 
     *  scrolling the viewport.
     *  This method calculates the amount to scroll by calling the 
     *  <code>IViewport.getVerticalScrollPositionDelta()</code> method 
