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   _____   _    _    __   __   __   __    ______  
  / ___// | || | ||  \ \\/ //  \ \\/ //  /_____// 
  \___ \\ | || | ||   \   //    \ ` //   `____ `  
  /    // | \\_/ ||   / . \\     | ||    /___//   
 /____//   \____//   /_//\_\\    |_||    `__ `    
`-----`     `---`    `-`  --`    `-`'    /_//     
                                         `-`

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發送短信 : Identification for difference in differences with cross-section and panel data