發送短信 : Convexity, geodetic, and hull numbers of the join of graphs

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