發送短信 : Positivity of Paneitz Operators

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