Adopt the following grammatical rules from "Longman English Grammar
    Practice (for intermediate students)" book:
    
        - We use apostrophe s ('s) and s apostrophe (s') for people and
          some living things to show possession: _Gus's car_, _the girls'
          shoes_, _a dog's bark_.
    
        - When we want to show possession with things, we can use _of_: _the
          leg of the table_. However, we often prefer to use a compound
          noun instead of _of_: _the table-leg_.
    
        - We can say _the voice of a man_ or _the man's voice_ (NOT _a man
          voice_).
    
        - We can say _the leg of a table_ or _a table-leg_ (NOT _a table's
          leg_).