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

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發送短信 : The compound equation related to the Bessel-Helmholtz equation and the Bessel-Klein-Gordon equation