EDIT
Use of character The copyright sign is used in combination with the copyright holder\'s name and the year of first publication and is conspicuously displayed. It is spaced (Copyright © 2004 by name), omission of the words »Copyright« and »by« is optional (© 2004 name).
Under no circumstances should the outdated notation (c) be used - it dates back to the times when the proper copyright sign was not yet available on computers (leave alone typewriters). See also
U+249E PARENTHESIZED LATIN SMALL LETTER C