下了个例子学习，在调试出现重复声明的错误，请教是什么原因？
interface

uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls,DateUtils,
  Vcl.Imaging.pngimage, Vcl.ExtCtrls , ExtCtrls , StdCtrls, Controls, Classes;


出现错误：
[dcc32 Error] uLogin.pas(8): E2004 Identifier redeclared: 'Vcl.ExtCtrls'
[dcc32 Error] uLogin.pas(8): E2004 Identifier redeclared: 'Vcl.Controls'