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  ______   __   __   __   _    __   __  __    __  
 /_   _//  \ \\/ // | || | ||  \ \\/ // \ \\ / // 
 `-| |,-    \ ` //  | '--' ||   \ ` //   \ \/ //  
   | ||      | ||   | .--. ||    | ||     \  //   
   |_||      |_||   |_|| |_||    |_||      \//    
   `-`'      `-`'   `-`  `-`     `-`'       `

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Text this: Terahertz conductivity of topological surface states in Bi1.5Sb0.5Te1.8Se1.2