def is_junk(c):
    """
    Return True if string `c` is a junk copyright that cannot be resolved
    otherwise by the parsing.
    It would be best not to have to resort to this, but this is practical.
    """
    junk = set([
        'copyrighted by their authors',
        'copyrighted by their authors.',
        'copyright holder or other authorized',
        'copyright holder who authorizes',
        'copyright holder has authorized',
        'copyright holder nor the author',
        'copyright holder(s) or the author(s)',

        'copyright owner or entity authorized',
        'copyright owner or contributors',

        'copyright for a new language file should be exclusivly the authors',

        'copyright holder or said author',
        'copyright holder, or any author',
        'copyrighted material, only this license, or another one contracted with the authors',
        'copyright notices, authorship',
        'copyright holder means the original author(s)',
        "copyright notice. timevar.def's author",

        "copyright holder or simply that it is author-maintained'.",
        "copyright holder or simply that is author-maintained'.",
        '(c) if you bring a patent claim against any contributor',
        'copyright-check writable-files m4-check author_mark_check',
        # 'copyrighting it yourself or claiming authorship'
    ])
    return c.lower() in junk