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

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