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  ______     ___     _    _      ___     __   _   
 /_____//   / _ \\  | |  | ||   / _ \\  | || | || 
 `____ `   | / \ || | |/\| ||  / //\ \\ | '--' || 
 /___//    | \_/ || |  /\  || |  ___  ||| .--. || 
 `__ `      \___//  |_// \_|| |_||  |_|||_|| |_|| 
 /_//       `---`   `-`   `-` `-`   `-` `-`  `-`  
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發送短信 : Power laws in the number of copies per title in libraries