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

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發送短信 : On Index 2 Subgroups of Hyperbolic Symmetry Groups