docs: function _fnGetUniqueThs ( oSettings, nHeader, aLayout )
  		{
  			var aReturn = [];
  			if ( !aLayout )
  			{
  				aLayout = oSettings.aoHeader;
  				if ( nHeader )
  				{
  					aLayout = [];
  					_fnDetectHeader( aLayout, nHeader );
  				}
  			}
  		
  			for ( var i=0, iLen=aLayout.length ; i<iLen ; i++ )
  			{
  				for ( var j=0, jLen=aLayout[i].length ; j<jLen ; j++ )
  				{
  					if ( aLayout[i][j].unique && 
  						 (!aReturn[j] || !oSettings.bSortCellsTop) )
  					{
  						aReturn[j] = aLayout[i][j].cell;
  					}
  				}
  			}
  			
  			return aReturn;
  		}