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The symbol isn't required by the leading copyright treaty, the Berne Copyright Convention (to which 181 countries belong, including the U.S.
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However, the symbol © is used universally to identify a work protected by copyright and to indicate its copyright owner. In most circumstances, the use of the copyright symbol isn't mandatory.
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Some people believe that if a work doesn't bear a copyright symbol, then that work isn't protected by copyright law. Why You Should Use the International Copyright Symbol
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A copyright symbol informs others that copyright exists in your work.
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