If at criminal proceedings at which an accused is charged with the unlawful publication of defamatory matter which is contained in a periodical, it is proved that such periodical or the part in which such defamatory matter is contained, was published by the accused, other writings or prints purporting to be other numbers or parts of the same periodical, previously or subsequently published, and containing a printed statement that they were published by or for the accused, shall be admissible in evidence without further proof of their publication.